Instructor Guide for Introduction

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October 1999

Instructor Guide forIntroduction to Oracle:SQL and PL/SQL


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Author

Priya Nathan

Copyright Oracle Corporation, 1999. All rights reserved.

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.....................................................................................................................................................Oracle Education Products 3

.....................................................................................................................................................Introduction

IntroductionIntroduction to Oracle: SQL and PL/SQL is often the first course that many Oracle students

attend. You might be their first contact with any Oracle personnel.

At the same time, this may be one of the first courses that you teach as an Oracle instructor, so

you might appreciate some help in achieving the best performance possible at an early stage ofyour career.

The tools and tips in this section come from the highly recommended AIT (Advanced

Instructional Techniques) class, which many Oracle Educaton instructors have attended. If

you attend that class, you will learn all that is hereand much more.

Aim of This Document

To help you make this the best technical course that students have ever attended, to excite

them to learn, and to make them want to come back for more

To give you some tips and techniques to help you vary your lecture style, avoid monotony

in classes, and make the learning experience more entertaining and interesting for both the

students and yourselfThis document is not a substitute for your own personal training and delivery instructions that

you receive from your Education department.

Using This Document

None of these suggestions and techniques are mandatory. They are simply examples of how to

introduce variety and change of pace into your classes.

Not all techniques suit all instructors. Choose those with which you feel most comfortable. If

possible, test the techniques with a fellow instructor who is also eager to encourage interactive

learning in the classroom.


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.....................................................................................................................................................4 Oracle Education Products

.....................................................................................................................................................

The Learning Environment

Introduction

Establish a pleasant and effective learning environment at the start of a class.

Tips to Improve the Class Climate

When students first arrive at a course, they have doubts, concerns, and fears. To change these

negative feelings to positive ones, try to make students feel welcome, safe, comfortable,

important, competent, understood, and responsible. Think carefully about what you can say

and do to foster these feelings of comfort and familiarity in your students, especially in the

first 30 minutes of the course.

Students learn more effectively in a physically and emotionally comfortable environment.

Early Arrivals

Some students arrive early for class. Do not ignore these studentswelcome them with a

smile. Make them feel comfortable by introducing yourself and providing details about the

class and the environment.

Housekeeping

Explaining the housekeeping ground rules at the start of a class is very important to make

students feel comfortable and confident in their surroundings. Remember to explain some of

the following points:

Layout of building: Point out the location of restrooms, refreshments, and so on.

Timing of class: State the start and end times and lunchtime.

Questions: Encourage students to ask questions during the class.

Personal Introductions

Allowing time for students to introduce themselves is important for you and for them. Whenyou know that course timings are tight, it is very tempting to reduce time allowed for

introductions or skip them altogether, but you do so at your peril. Introductions help foster a

good relationship between all the students.

Use introductions to find out more about your audience: those who might not have sufficient

prerequisite knowledge, those who might cause problems because they are eager to prove

themselves in front of others, and so on.

Thought for the Day

Never do for the learners what they can do for themselves.

Efficient Use of Icebreakers

You can use icebreakers successfully throughout the course. At the beginning of a class: Choose something that helps students get to know others in the

class.


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.....................................................................................................................................................The Learning Environment

After break times: Occupy and entertain those who return early from breaks.

Afternoon: Avoid the graveyard-shift syndrome. Give students a short, light activity to

refresh them after lunch or in the late afternoon.

Icebreakers to Use in Class Introductions

You can vary your class introductions with either of these icebreakers:

Partner Introductions

Ask each person to select a partner who is a stranger to them.

Give ten minutes for partners to interview each other and find out as much as possible

about each other.

Suggest that they take notes during their interviews.

After the interviews, ask each person to stand in turn and introduce their partner to the

entire group (encourage them to refer to their notes).

Note: This icebreaker works best with smaller groups (fewer than 20). For larger groups,

it is too time-consuming.

Icebreakers for After-Lunch Activity

Try using one of these to wake up the group after lunch:

Common Ground

Use this icebreaker for small groups or for each small group sitting together as a team

(example: four to six people).

Give the groups a specific time (example: five minutes) to list everything they can find

that they all have in common. Tell them to avoid the obvious (example: we are all taking

this workshop). Ask them to make a list.

After the time is up, ask each group how many items they have in their list.

For fun, ask them to announce some of the most interesting items in their lists.

Dreams and Nightmares

Each person states a dream about something positive that they hope will happen in this

course.

Each person states a nightmare about something negative that they hope will not happen in

this course.

Put the dreams and nightmares on a flip chart so all groups can read them.

Notice that most of these icebreakers are brief exercises that focus on getting to know the

people they will work with. If groups are changed regularly, start each session with a different

icebreaker.


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Lecture Styles

Keywords

As you speak, write keywords on a flip chart to create an emerging content outline.

When you fill a page, tape it to the wall and start a new one on the flipchart. Put no more than seven keywords on a page.

When finished, ask the students to review by recalling the content that is triggered by each

keyword. The review can be an individual exercise or it can be done through discussion in

small groups.

Cartoon Lecture

Find cartoons that relate to the content of your lecture. Transfer the cartoons onto

overhead transparencies.

For each key point in the lecture, show the cartoon after you have described the content

verbally.

When the lecture is finished, show each cartoon again and have the students review thecontent using the cartoon as a mental trigger. The review can be an individual exercise or

it can be done through discussion in groups.

The mind is like the stomach. Its not how much you put into it that counts, but how much it

digests.

Examples and Exceptions

Good lectures often contain examples, analogies, and metaphors.

As you deliver a lecture, ask students in small groups to create an example or analogy of

the point you are describing.

For a change of pace, ask them to create exceptions to the point.

Encourage learners to use situations from their own experience as the source for examples,

where possible.

Fill in the Blank

Design a printed outline of the key ideas to be covered in the lecture.

Leave out a word or short phrase in each item in the outline.

As you lecture, ask students to fill in the missing words.

Before I speak, I have something important to say. Groucho Marx

Search and Learn

Rather than deliver a lecture, put the content in printed form. Use headings and bullets

rather than paragraphs.

Give learners a series of questions to answer by searching through the printed material. If

you want a competitive element, have small groups search quickly for the answer. The

group that finds it first raises their hands and announces the location of the answer. If they


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.....................................................................................................................................................Lecture Styles

are correct, they receive a point. At the end, you could have a prize for the winning group.

Forming Effective Questions

The following points will help you to make your questioning more effective:

Employ the characteristics of a good question: Concise and contains only one idea

Thought provoking and interesting

Focused on important material

Open-ended (requires more than a yes or no answer)

Requires reasoning rather than memory

Challenging but answerable

Four directions for questions:

Direct: Ask a specific student.

Overhead: Ask the students in general; anyone can answer.

Relay: Ask someone else to answer a students question.

Reverse: Mirror a students question back to the same student.

Do not repeat students answers. Otherwise, students may stop listening to each other.

Use crossfire questioning. Refer questions to others, such as:

How would you have answered that?

Why do you think that?

What do you think of that answer?

What evidence do you have for that?

When answering a question, use these techniques:

When someone asks you a question, smile, take a step toward them, and say yes as

if you are pleased to have a question.

Check to be sure everyone heard and understood the question.

Answer briefly and state reasons for your answer.

Tie your answer to key points in your lesson, if possible.

If you do not know an answer, admit itnever bluff. Ask if anyone else knows the

answer. If no one does, offer to find out.

If someone asks a contentious question, give a direct and friendly answer. Do not be

provoked into a defensive position.

If someone asks a question that you will be covering later, say Thats a good

question. We will be covering that in a few minutes.


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.....................................................................................................................................................

BibliographyEitlington, Julius. The Winning Trainer. Gulf Publishing, 1984.

Forbess-Green, Sue.Encyclopedia of Icebreakers . University Associates, 1990.

Jones, Philip (ed.).Adult Learning in Your Classroom. Lakewood Publications,

1982.

Newstrom, John, and Edward Scannell. Games Trainers Play. McGraw-Hill, 1980.

OConnor, Joseph, and John Seymour.Introducing Neuro-Linguistic

Programming. Thorsons, 1995.

OConnor, Joseph, and John Seymour. Training with NLP. Thorsons, 1994.

Pike, Robert. Creative Training Techniques Handbook. Lakewood Publications,

1989.

Scannell, Edward, and John Newstrom.More Games Trainers Play. McGraw-Hill,

1991.


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.....................................................................................................................................................About the Course

About the Course

Lesson Objectives and Aims

Each lesson starts with an objectives page that describes the reasons for the lesson; there is

also an objectives slide that should be used. The intention of each lesson should be clear to

everyonelecturer and studentsat the start of every lesson.

The topics covered in each lesson should give students enough information to complete the

required part of each practice.

Lesson Timings

If a lesson drags on, for whatever reason (yes there will be those exceptions) then break the

lesson for five minutes. Give everyone a rest.

Practices

Practices are as important as the lesson. Practice timings are usually the same as or more than

the lecture time allowance, to ensure that the students get as much exposure to the product as

possible.The "If you have time" questions are there for those who need a challenge; for example, for

students who already have SQL knowledge or are finding the subject easy. What questions

students are expected to complete is made clear in the table at the start of each practice.

Enforcing Learning Points

Consider the following ideas when teaching:

Always use the lesson objectives slide to stress the intention of the lesson, and use the

summary slide to reiterate learning points.

Invite student questions at all times.

At the start of a new day, spend 5 minutes of your time to remind students of the topics

covered the previous day. No detail is required, this is just a memory-jogging session. Do not discuss syntax slides word-for-word. Identify and discuss the main learning points.

In most cases, students have an opportunity to use the syntax during the practices.

Practice Sessions

Some practices, contain "if you want extra challenge" questions. Let the student do these only

if you they have completed all of the other questions within the allocated time and would like

a further challenge to their skills.

Demonstrations

Do not show slides and demonstrate for each slide; use demonstrations to stress learning

points:

There is not enough time.

Students get bored watching the lecturer doing all the work and having all the fun, it


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seems, when they are itching to get their hands on the product.

You can use the Class Management Notes to assist you when teaching the courses. This

document has been constructed to try to help instructors identify what the main learning

points are for any lesson.

You can present the course without any demonstration at all.

Interaction

Ensure the students are aware that the course is interactive. As much as you are there to teach,

the students are there to understand, assimilate, and experiment. If they do not understand

anything that is presented, they should ask questions. Students should not be afraid to ask

questions, or be worried as to whether the questions are relevant. Of course some questions

may be beyond the scope of the course (if that is the case, say so) or beyond the scope of your

knowledge.

Appendixes and Answers

Clearly identify which appendixes are available and where to find them in the manual and

specifically where to find the practice demostrate tables and practice solutions.

Snippets

This course includes animation and activity snippets. A description of these snippets can be

found in Snipdesc.doc along with the other lessons for this course.

Structure of the Instructor Guide

Element Description

Additional information Additional information that the instructor can

share in class

Hint A hint to the instructor with specific reference tothe slide

Additional example An additional example to explain in class

Additional reference Where the instructor can look up additional

information related to the subject of the slide


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.....................................................................................................................................................Introduction

Introduction

Additional Information

If time permits, share the following

information with the class. Structured

systems analysis and design helps in

understanding and designing a system,

which will be programmed later in any

programming language. It is the stepping

stone in creating simple or large, critical-

mission, complex systems. During this

stage, you will learn how to put down on

paper a large, complex system in a short

and understandable manner that can be

understood by any lay person.

Beginning with strategy and analysis, theproject teams objective is to identify the

high-level requirements and develop a

conceptual scope of work. This

information is used to develop the

preliminary cost and time requirements. It

also serves as the foundation for the

remaining phases.

The design phase facilitates the design of

all system components. This includes the

user interface, database model, report

layout, business rules, systems interfacing,

and documentation. In essence, the projectteam creates the blueprints for the

development of the system.

Prototyping may be performed to help

facilitate the design and transition phases

and ensure the validity of business rules,

determine the feasibility of technical

options, and help to expose the value of

the comprehensive information

management system.

System Development Life Cycle

Strategyand

AnalysisDesign

Buildand

Document

Transition

Production


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.....................................................................................................................................................

(continued) Transition is the process of applying

technology, skill, and development

standards to the design specifications.

Testing involves the validation of all

system components to ensure that theproduct operates and performans in

accordance with the design specifications.

QA audits, client reviews, quality

certification, implementation planning,

installation, setup, and training are

included in the production and rollout

phase.

A flexible support and maintenance plan

may include phone support,

troubleshooting, planned upgrades, and

enhancements.



information with the class. A relational set

is often modeled as a table. The items of a

set are the rows of the table. The fields in

the items are the columns. The columns in

a table can have names. The rows are

unordered and unnamed. A database

consists of one or more tables plus a

catalog (also represented by tables)

describing the database.

Relational Database Concept

Dr. E. F. Codd proposed the relational modelfor database systems in 1970.

It is the basis for the relational databasemanagement system (RDBMS).

The relational model consists of the following:

Collection of objects or relations

Set of operators to act on the relations

Data integrity for accuracy and consistency


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.....................................................................................................................................................Introduction



information with the class. The relational

model presents an orderly, predictable,

and intuitive approach to organizing,manipulating, and viewing data.

Relational tables have six properties,

which must be satisfied for any table to be

classified as relational. These are:

Entries of attributes are single-valued.

Entries in every row and column

position in a table must be single-

valued. This means columns do not

contain repeating groups.

Entries of attributes are of the same

kind.Entries in a column must be of the

same kind. For example, a column

that stores salary information should

not be used to store commission

information.

No two rows are identical.

Each row should be unique. This

uniqueness is ensured by the values in

a specific set of columns called the

primary key.

The order of attributes is unimportant.There is no significance attached to

the order in which columns are stored

in the table. A user can retrieve

columns in any order.

The order of rows is unimportant.

There is no significance attached to

the order in which rows are stored in

the table. A user can retrieve rows in

any order.

Every column can be uniquely

identified.

Each column is identified by its name

and not its position. A column name

should be unique in the table.

Definition of aRelational Database

A relational database is a collection ofrelations or two-dimensional tables.

Database

DEPTNO DNAME LOC

10 ACCOUNTING NEW YORK

20 RESEARCH DALLAS

30 SALES CHICAGO

40 OPERATIONS BOSTON

DEPTNO DNAME LOC


20 RESEARCH DALLAS

30 SALES CHICAGO


Table Name: DEPT

EMPNO E NAME JOB DEP TNO

7839 KING PRESIDENT 10

7698 BLAKE MANAGER 30

7782 CLARK MANAGER 10

7566 JONES MANAGER 20

EMPNO E NAME JOB DEPTNO





Table Name: EMP


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Additional Reference

http://cis.csustan.edu/courses/

lodewyck/4720/ERModel/index.htm

http://coba.usf.edu/trimmer/

Chap3/index.htmhttp://www.musc.edu/hap/

Phoenix3/index.htm

Create an entity relationship diagram frombusiness specifications or narratives

Scenario

. . . Assign one or more employees to adepartment . . .

. . . Some departments do not yet haveassigned employees . . .

Entity Relationship Model

EMPLOYEE#* number* nameo job title

EMPLOYEE#* number* nameo job title

DEPARTMENT#* number* name

o location

DEPARTMENT#* number* nameo location

assigned to

composed of


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.....................................................................................................................................................Introduction



information with the class. Object

orientation is the use of objects and classes

in analysis, design, and programming. Theuse of objects distinguishes object

orientation from other techniques such as

traditional structured methods (process-

based: data and function are separate) or

other techniques such as knowledge-based

systems (logic programming, rules:

Prolog) or mathematical methods.

Object orientation is:

View Of The World - A Better

Approach

ProcessIterative/Incremental - Easy to add to

systems

Methods

Analysis

Design

Implementation

Languages

Programming Technique

Object-oriented programming languages

provide full support for object design.


http://www.cyberdyne-object-

sys.com/oofaq2/

Oracle8: Object RelationalDatabase Management System

User-defined data types and objects

Fully compatible with relationaldatabase

Support of multimedia and large objects

High-quality database server features


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http://www.cyberdyne-object-

sys.com/oofaq2/

Data Models

Model ofsystem

in clientsmind

Entity model ofclients model

Table modelof entity model

Tables on disk

Server


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.....................................................................................................................................................Introduction


If time permits, share this information

with the class. PL/SQL is the procedural

extension to SQL, provided by Oracle.

Through PL/SQL, the data manipulationcapabilities of SQL are combined with the

processing capabilities of a procedural

language. PL/SQL provides features like

conditional execution, looping, and

branching. PL/SQL supports subroutines

too. The basic unit in any PL/SQL

program is a block, which can occur

sequentially (one after the other) or nested

(one inside the other). Using PL/SQL you

can write subprograms, procedures,

packages, and functions that are stored in

the database.

Hint

One of the ways of introducing PL/SQL to the class is by explaining the capabilities that

SQL lacks and how PL/SQL serves as an extension to SQL. The objective of this slide is to

highlight that PL/SQL combines the data manipulating power of SQL with the data

processing power of procedural languages.

The Problem: SQL is the most powerful and comprehensive database language, that enables

you to create, organize, retrieve and maintain data stored in a database. But it does not

provide the features which a typical programming language offers, such as control-of-flow

constructs (sequence, selection and iteration constructs), or the facility to define and use

variables. SQL has a more set based approach. It returns a set of rows after a query is

executed.

The Solution: The solution is PL/SQL, which is a language that has the programming

features that SQL lacks. It provides control-of-flow constructs and lets you declare and use

variables. PL/SQL gives the flexibility of row-wise access to the records in the underlying

table.


http://st-doc.us.oracle.com/8.0/815/server.815/a67842/

01_oview.htm#651

About PL/SQL

PL/SQL is an extension to SQL with

design features of programminglanguages.

Data manipulation and query statementsof SQL are included within proceduralunits of code.


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Hint

Draw attention to the fact that PL/SQL can

reside in two environments:

The Oracle Server Oracle Tools

Explain the diagram on the slide as

follows: The diagram shows the PL/SQL

engine processing an anonymous block.

The engine executes procedural

statements but sends SQL statements to

the SQL statement executor in the Oracle

server.


http://st-doc.us.oracle.com/

8.0/815/server.815/a67842/

01_oview.htm#962

PL/SQL Environment

PL/SQLblock

PL/SQL engine

Oracle Server

ProceduralStatementExecutor

PL/SQL

SQL

SQL Statement Executor

PL/SQLblock


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.....................................................................................................................................................Lesson 1: Writing Basic Select Statements

Lesson 1: Writing Basic Select Statements


Explain that selection retrieves only

selected rows, projection retrieves only

selected columns and joins can retrieve

rows, columns, or both depending on the

SELECT clause.

Hint

If time permits, you can include the

explanation of other relational operators

like PRODUCT, INTERSECTION, and

DIFFERENCE.

PRODUCT: the result of a query that

concatenates rows from two sets of data.

All rows in the first set are concatenatedwith all rows in the second set, often

producing a very large new set.

INTERSECTION: displays all rows that

appear in both of two relations.

DIFFERENCE: displays rows that appear

in one relation only. (SQL uses operator

minus.)

Hint

Explain that all clauses mentioned within

[ ] are optional. Also mention that other

clauses like GROUP BY and ORDER BYare also part of a SELECT statement and

will be explained in the later lessons.

Capabilities of SQL SELECTStatements

Selection Projection

Table 1 Table 2

Table 1 Table 1Join

Basic SELECT Statement

SELECT [DISTINCT] {*, column [alias],...}

FROM table;


FROM table;

SELECT identifies whatcolumns.

FROM identifies whichtable.


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Hint

Point out that using tabs and indents, and

placing different clauses on separate lines

I increases readability of the SQL

statement.

Hint

Revisit slide 4 here. Explain SELECT and

FROM as keywords here.

Highlight that this is not a projection as allcolumns are being selected.

Hint

Highlight that this is a projection as only

the selected columns are being displayed.Also all rows are selected.

Basic SELECT Statement


FROM table;


FROM table;

SELECT identifies whatcolumns.

FROM identifies whichtable.

Selecting All Columns

DEPTNO DNAME LOC

--------- -------------- -------------


20 RESEARCH DALLAS

30 SALES CHICAGO


SQL> SELECT *

2 FROM dept;

Selecting Specific Columns

DEPTNO LOC

--------- -------------

10 NEW YORK

20 DALLAS

30 CHICAGO

40 BOSTON

SQL> SELECT deptno, loc

2 FROM dept;


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Hint

Highlight that the case of the columns

specified in the SELECT list does not

influence the case of the headings in the

results set. Mention that these headingscan be customized and will be covered in

the subsequent slides.

Hint

The explanation can include that

sometimes there is a requirement to

perform certain calculations with the datafrom the tables. Highlight that these

calculated values can be displayed on the

screen or used to update the data in the

underlying tables. Mention that arithmetic

operators cannot be used in the FROM

clause.



8.0/815/server.815/a67779/

operator.htm#997746

Hint

Explain that an expression is a

combination of one or more values,

operators, and functions that evaluate to a

value. Highlight that SQL*PLUS ignores

blank spaces before and after the

arithmetic operators.

Column Heading Defaults

Default justification

Left: Date and character data

Right: Numeric data

Default display: Uppercase

Arithmetic Expressions

Create expressions on NUMBER and DATEdata by using arithmetic operators.

Operator

+

-

*

/

Description

Add

Subtract

Multiply

Divide

Using Arithmetic Operators

SQL> SELECT ename, sal, sal+300

2 FROM emp;

ENAME SAL SAL+300

---------- --------- ---------

KING 5000 5300

BLAKE 2850 3150

CLARK 2450 2750

JONES 2975 3275

MARTIN 1250 1550

ALLEN 1600 1900

...

14 rows selected.


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.....................................................................................................................................................

Hint

Explain that if your arithmetic expression

contains more than one operator, the

priority is *, / first then +, -. (left to right if

there are several operators with the samepriority).

Hint

Mention that only one kind of parenthesis

( ) is accepted as part of SQL*Plus syntax.

Additional Example

Explain the difference between in the

output of these two SELECT statements:

SELECT ename, sal + 250 * 12

FROM emp;

SELECT ename, (sal + 250) *

12

FROM emp;

Hint

Mention that no two NULLS compare as

equal. Demonstrate the structure of the

EMP table and highlight that the EMPNO

has been defined as NOT NULL, so no

NULLs will be accepted. Explain that this

will be addressed in detail in the later

lessons.



8.0/815/server.815/a67779/

ch2.htm#4008

Operator Precedence

Multiplication and division take priorityover addition and subtraction.

Operators of the same priority areevaluated from left to right.

Parentheses are used to forceprioritized evaluation and to clarifystatements.

* / +_

Using Parentheses

SQL> SELECT ename, sal, 12*(sal+100)

2 FROM emp;

ENAME SAL 12*(SAL+100)

---------- --------- -----------

KING 5000 61200

BLAKE 2850 35400

CLARK 2450 30600

JONES 2975 36900

MARTIN 1250 16200

...

14 rows selected.

Defining a Null Value

A null is a value that is unavailable,unassigned, unknown, or inapplicable.

A null is not the same as zero or a blankspace.

SQL> SELECT ename, job, comm

2 FROM emp;

ENAME JOB COMM

---------- --------- ---------

KING PRESIDENT

BLAKE MANAGER

...

TURNER SALESMAN 0

...

14 rows selected.


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Hint

Highlight that including a NULL column

value in an arithmetic expression will give

wrong results, though SQL*PLUS will not

report any error. We might be fooled bythe erroneous results.


Oracle SQL Reference Manual, Release 8,

Elements of SQL

Hint

Explain that column aliases produce more

readable and meaningful output. You can

have descriptive column aliases. You canset the case of the column alias to lower

case, mixed case, or upper case. Highlight

that you cannot use column aliases in a

WHERE clause and that a column alias

does not change the actual name of the

column. Mention that column aliases can

be generated using both AS and by using

double quotes.

Hint

Explain the use of the double quotes and

that you must use them if the column aliascontains a space.

Null Valuesin Arithmetic Expressions

Arithmetic expressions containing a null

value evaluate to null.

SQL> select ename, 12*sal+comm

2 from emp

3 WHERE ename=KING;

ENAME 12*SAL+COMM

---------- -----------

KING

Defining a Column Alias

Renames a column heading Is useful with calculations

Immediately follows column name;optional AS keyword between columnname and alias

Requires double quotation marks if itcontains spaces or special charactersor is case sensitive

Using Column Aliases

SQL> SELECT ename AS name, sal salary2 FROM emp;

NAME SALARY

------------- ---------

...

SQL> SELECT ename "Name",

2 sal*12 "Annual Salary"

3 FROM emp;

Name Annual Salary

------------- -------------

...


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.....................................................................................................................................................

Hint

Highlight that the resulting value is a

character value. Ask the participants to

note that the symbol for the concatenation

operator is ||.



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operator.htm#997790

Additional Example

SELECT

substr(ename,1,1)||empno

Email IDFROM emp;

The result set will now contain the first

character of the employees name

concatenated with his employee number.

For example, the e-mail ID for King will

be K7839. Explain the SUBSTR function

in brief.

Hint

Highlight that the literal is a part of every

row of the results set. Literal characterstrings can be used to generate reports.



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ch2.htm#3305

Concatenation Operator

Concatenates columns or character

strings to other columns Is represented by two vertical bars (||)

Creates a resultant column that is acharacter expression

Using the ConcatenationOperator

SQL> SELECT ename||job AS "Employees"

2 FROM emp;

Employees

-------------------

KINGPRESIDENT

BLAKEMANAGER

CLARKMANAGER

JONESMANAGER

MARTINSALESMAN

ALLENSALESMAN

...

14 rows selected.

Literal Character Strings

A literal is a character, expression, ornumber included in the SELECT list.

Date and character literal values mustbe enclosed within single quotationmarks.

Each character string is output once foreach row returned.


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Hint

Revisit the concatenation operator here.

Explain how a space can be a part of the

results set by enclosing a space between

two single quotes. Revisit column aliashere.

Hint

Alternatively to get a list of the unique

departments, they can select DEPTNO

from the DEPT table.

Additional Example

SELECT job

FROM emp;

Additional Example

SELECT DISTINCT(job)

FROM emp;

Using Literal Character Strings

Employee Details

-------------------------

KING is a PRESIDENT

BLAKE is a MANAGER

CLARK is a MANAGER

JONES is a MANAGER

MARTIN is a SALESMAN

...

14 rows selected.

SQL> SELECT ename || ||is a|| ||job

2 AS "Employee Details"

3 FROM emp;

Duplicate Rows

The default display of queries is all rows,

including duplicate rows.SQL> SELECT deptno

2 FROM emp;

SQL> SELECT deptno

2 FROM emp;

DEPTNO

---------

10

30

10

20

...

14 rows selected.

Eliminating Duplicate Rows

Eliminate duplicate rows by using theDISTINCT keyword in the SELECT clause.

SQL> SELECT DISTINCT deptno

2 FROM emp;

DEPTNO

---------

10

20

30


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.....................................................................................................................................................

Hint

Give an overview of all the uses of the

SQL statements. Explain SQL as a

nonprocedural language. It does not

support procedural constructs like IF,LOOP, etc. Explain SQL*Plus commands

as being very useful to modify the

command in the buffer, without which we

would have to retype the entire command

again or use an editor.



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ch1.htm#216

HintFor SQL commands, demostrate:

How the lines are automatically

numbered as they are entered

How commands cannot be

abbreviated. Type a keyword,

abbreviated command, and demostrate

the error message

Both the termination characters ; and /

Some simple case functions like

upper() and lower()

How to rerun a command from thebuffer using RUN or /

For SQL*Plus commands, mention a few

commonly used commands like

A[PPEND], C[HANGE], and so on and

say they will be discussed in detail as you

proceed in the same lesson.

SQL and SQL*Plus Interaction

SQL*Plus

SQL StatementsBuffer

SQL Statements

Server

Query ResultsSQL*PlusCommands

Formatted Report

SQL Statements VersusSQL*Plus Commands

SQLstatements

SQL

A language

ANSI standard

Keyword cannot beabbreviated

Statements manipulatedata and tabledefinitions in thedatabase

SQL*Plus

An environment

Oracle proprietary

Keywords can beabbreviated

Commands do notallow manipulation ofvalues in the database

SQLbuffer

SQL*Pluscommands

SQL*Plusbuffer


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Hint

Explain the main categories of the

SQL*Plus commands: environment,

format, file manipulation, execution, edit,

interaction, miscellaneous (as in notespages).

Hint

Explain the scott/tiger account.

Explain that the password is not case-

sensitive. Explain the host string. If thefacility permits, demostrate how to use

SQL*Net easy configure or Net8 (if you

are using Oracle8) to configure a database

alias name.

Hint

Explain that DESC will also work. Also

include that the DESC is mandatory andeven something like DESCRI would

work.

SQL Statements VersusSQL*Plus Commands

SQLstatements

SQL

A language

ANSI standard

Keyword cannot beabbreviated

Statements manipulatedata and tabledefinitions in thedatabase

SQL*Plus

An environment

Oracle proprietary

Keywords can beabbreviated

Commands do notallow manipulation ofvalues in the database

SQLbuffer

SQL*Pluscommands

SQL*Plusbuffer

Logging In to SQL*Plus

From Windows environment:

From command line:

sqlplus [username[/password

[@database]]]

Displaying Table Structure

Use the SQL*Plus DESCRIBE command todisplay the structure of a table.

DESC[RIBE] tablenameDESC[RIBE] tablename


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.....................................................................................................................................................

Hint

Revisit NOT NULL. Review the datatypes

shown in brief.

Additional Referencehttp://st-doc.us.oracle.com/

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ch2.htm#3463

Hint

Demostrate the commands on the slide.

Displaying Table Structure

SQL> DESCRIBE deptSQL> DESCRIBE dept

Name Null? Type

----------------- -------- ------------

DEPTNO NOT NULL NUMBER(2)

DNAME VARCHAR2(14)

LOC VARCHAR2(13)

SQL*Plus Editing Commands

A[PPEND] text C[HANGE] / old/ new

C[HANGE] / text/

CL[EAR] BUFF[ER]

DEL

DEL n

DEL m n


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Hint


Hint


SQL*Plus Editing Commands

I[NPUT]

I[NPUT] text

L[IST]

L[IST] n

L[IST] m n

R[UN]

n

ntext

0 text

SQL*Plus File Commands

SAVE filename GET filename

START filename

@ filename

EDIT filename

SPOOL filename


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.....................................................................................................................................................

Lesson 2: Restricting and Sorting Data

Hint

Revisit selection. Mention that all

columns are retrieved unless explicitly

specified.

Hint

Explain that the WHERE clause should

start on a separate line to increase

readability. Explain that the WHERE

clause consists of the column name,

comparison operator, and condition.

Mention that there can be more than one

condition and this will be explained later

in the lesson.

5

Hint

Explain that the condition is case-

sensitive. Also explain that characters and

dates, when included as part of the

condition, should be enclosed within

single quotes.

Additional Example

WHERE job = Clerk

Demostrate a condition with clerk in

mixed/lower/title case and show that there

are no rows selected.

Limiting Rows Using a Selection

"retrieve allemployees

in department 10"

EMP

EMPNO ENAME JOB ... DEPTNO





...

EMP

EMPNO ENAME JOB ... DEPTNO

7839 KING PRESIDENT 107782 CLARK MANAGER 10

7934 MILLER CLERK 10

Limiting Rows Selected

Restrict the rows returned by using theWHERE clause.

The WHERE clause follows the FROMclause.

SELECT [DISTINCT] {*| column [alias], ...}

FROM table

[WHERE condition(s)];

Using the WHERE Clause

SQL> SELECT ename, job, deptno

2 FROM emp

3 WHERE job=CLERK;

ENAME JOB DEPTNO

---------- --------- ---------

JAMES CLERK 30

SMITH CLERK 20

ADAMS CLERK 20

MILLER CLERK 10


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.....................................................................................................................................................Lesson 2: Restricting and Sorting Data

6

Hint

Explain that date formats are also

sensitive, and the default is DD-MON-

YY. Highlight that MON is not case-

sensitive. Explain that case sensitivity canbe overridden using UPPER and LOWER

functions, which will be covered in the

later lessons.

Hint

Explain that in a >= or = or SELECT ename, job, deptno

2 FROM emp

3 WHERE ename = JAMES;

SQL> SELECT ename, job, deptno

2 FROM emp

3 WHERE ename = JAMES;

Comparison Operators

Operator

=

>

>=

SELECT ename, sal

2 FROM emp

3 WHERE sal BETWEEN 1000 AND 1500;

Lowerlimit

Higherlimit

Use the BETWEEN operator to displayrows based on a range of values.

Using the IN Operator

Use the IN operator to test for values in a

list.

SQL> SELECT empno, ename, sal, mgr

2 FROM emp

3 WHERE mgr IN (7902, 7566, 7788);

EMPNO ENAME SAL MGR

--------- ---------- --------- ---------

7902 FORD 3000 7566

7369 SMITH 800 7902

7788 SCOTT 3000 7566

7876 ADAMS 1100 7788


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Hint

Explain that it can be used with the

NUMBER, VARCHAR2, CHAR, and

DATE datatypes. You might want to draw

an analogy to the DOS ? and * wildcardsto help understanding.

Additional Example

SELECT *

FROM emp

WHERE hiredate

LIKE __-JAN%;

Hint

Demostrate the use of the ESCAPE

character.

Hint

Explain that it would be a good idea to use

the NVL function and check for a field forNULL values before including the field in

any calculations.

Using the LIKE Operator

Use the LIKE operator to performwildcard searches of valid search string

values. Search conditions can contain either

literal characters or numbers.

% denotes zero or many characters.

_ denotes one character.

SQL> SELECT ename

2 FROM emp

3 WHERE ename LIKE S%;

Using the LIKE Operator

You can combine pattern-matchingcharacters.

You can use the ESCAPE identifier tosearch for "%" or "_".

SQL> SELECT ename

2 FROM emp

3 WHERE ename LIKE _A%;

ENAME

----------

MARTIN

JAMES

WARD

Using the IS NULL Operator

Test for null values with the IS NULLoperator.

SQL> SELECT ename, mgr

2 FROM emp

3 WHERE mgr IS NULL;

ENAME MGR

---------- ---------

KING


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.....................................................................................................................................................

Hint

Revisit case sensitivity and use of quotes.

Explain what happens if a NULL value is

encountered. Explain the truth table in the

notes pages.



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operator.htm#998054

Hint

Revisit case sensitivity and use of quotes.

Explain what happens if a NULL value is

encountered. Explain the truth table in thenotes pages.

Hint

Revisit case sensitivity, use of quotes

Explain what happens if a NULL value isencountered. Explain the truth table in the

notes pages.



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operator.htm#998054

Using the AND Operator

AND requires both conditions to be TRUE.

SQL> SELECT empno, ename, job, sal2 FROM emp

3 WHERE sal>=1100

4 AND job=CLERK;

EMPNO ENAME JOB SAL

--------- ---------- --------- ---------

7876 ADAMS CLERK 1100

7934 MILLER CLERK 1300

Using the OR Operator

OR requires either condition to be TRUE.SQL> SELECT empno, ename, job, sal

2 FROM emp

3 WHERE sal>=1100

4 OR job=CLERK;

EMPNO ENAME JOB SAL

--------- ---------- --------- ---------





7654 MARTIN SALESMAN 1250

...

7900 JAMES CLERK 950

...

14 rows selected.

Using the NOT Operator

SQL> SELECT ename, job

2 FROM emp

3 WHERE job NOT IN (CLERK,MANAGER,ANALYST);

ENAME JOB

---------- ---------

KING PRESIDENT

MARTIN SALESMAN

ALLEN SALESMAN

TURNER SALESMAN

WARD SALESMAN


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Hint

Explain that usaging parenthesis increases

readability.

Additional Referencehttp://st-doc.us.oracle.com/

8.0/815/server.815/a67779/

operator.htm#997667

Hint


readability.

Hint


readability.

Rules of Precedence

Override rules of precedence by usingparentheses.

Order Evaluated Operator

1 All comparisonoperators

2 NOT

3 AND

4 OR

Rules of Precedence

ENAME JOB SAL

---------- --------- ---------

KING PRESIDENT 5000

MARTIN SALESMAN 1250

ALLEN SALESMAN 1600

TURNER SALESMAN 1500

WARD SALESMAN 1250

ENAME JOB SAL

---------- --------- ---------

KING PRESIDENT 5000

MARTIN SALESMAN 1250

ALLEN SALESMAN 1600

TURNER SALESMAN 1500

WARD SALESMAN 1250

SQL> SELECT ename, job, sal

2 FROM emp3 WHERE job=SALESMAN

4 OR job=PRESIDENT

5 AND sal>1500;

Rules of Precedence

ENAME JOB SAL

---------- --------- ---------

KING PRESIDENT 5000

ALLEN SALESMAN 1600

ENAME JOB SAL

---------- --------- ---------

KING PRESIDENT 5000

ALLEN SALESMAN 1600

Use parentheses to force priority.

SQL> SELECT ename, job, sal

2 FROM emp

3 WHERE (job=SALESMAN

4 OR job=PRESIDENT)

5 AND sal>1500;


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.....................................................................................................................................................

Hint

Explain that by default the results set is in

the same order as the order in which the

records where input into the table. ASC is

specified implicitly. You can order by acolumn alias. You can order by a column

that is not there in the SELECT list.

Hint

Explain the order of output for every

datatype: numbers, dates, character, and

null.

Hint

You might want to use the within-which.

For example, the results set is sorted byDEPTNO, within-which it is sorted by

SAL.

ORDER BY Clause Sort rows with the ORDER BY clause

ASC: ascending order, default

DESC: descending order

The ORDER BY clause comes last in theSELECT statement.

SQL> SELECT ename, job, deptno, hiredate

2 FROM emp

3 ORDER BY hiredate;

ENAME JOB DEPTNO HIREDATE

---------- --------- --------- ---------

SMITH CLERK 20 17-DEC-80

ALLEN SALESMAN 30 20-FEB-81

...

14 rows selected.

Sorting in Descending Order

SQL> SELECT ename, job, deptno, hiredate

2 FROM emp3 ORDER BY hiredate DESC;

ENAME JOB DEPTNO HIREDATE

---------- --------- --------- ---------

ADAMS CLERK 20 12-JAN-83

SCOTT ANALYST 20 09-DEC-82

MILLER CLERK 10 23-JAN-82

JAMES CLERK 30 03-DEC-81

FORD ANALYST 20 03-DEC-81

KING PRESIDENT 10 17-NOV-81

MARTIN SALESMAN 30 28-SEP-81

...

14 rows selected.

Sorting by Multiple Columns

The order of ORDER BY list is the order ofsort.

You can sort by a column that is not in theSELECT list.

SQL> SELECT ename, deptno, sal

2 FROM emp

3 ORDER BY deptno, sal DESC;

ENAME DEPTNO SAL

---------- --------- ---------

KING 10 5000

CLARK 10 2450

MILLER 10 1300

FORD 20 3000

...

14 rows selected.


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.....................................................................................................................................................Lesson 3: Single-Row Functions

Lesson 3: Single-Row Functions

Hint

Explain that a function is a built-in

formula that can accept one or more

arguments and returns one value as a

result.

4


Oracle Server SQL Reference, Release 8,

for the complete list of available functions

and syntax.



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function.htm#1028572

SQL Functions

FunctionInput

arg 1

arg 2

arg n

Functionperforms action

Output

Resultvalue

Two Types of SQL Functions

Functions

Single-rowfunctions

Multiple-rowfunctions

Single-Row Functions

Manipulate data items

Accept arguments and return one value

Act on each row returned

Return one result per row

May modify the datatype

Can be nested

function_name(column|expression, [arg1, arg2,...])function_name(column|expression, [arg1, arg2,...])


38/174


.....................................................................................................................................................

Hint

Explain the input that each of these

functions accept and the output (datatype)

that they return



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8.0/815/server.815/a67779/function.htm#1028572

Single-Row Functions

Conversion

Character

Number

Date

GeneralSingle-rowfunctions

Character Functions

Character

functions

LOWER

UPPER

INITCAP

CONCAT

SUBSTR

LENGTH

INSTR

LPAD

Case conversionfunctions

Character manipulationfunctions

Function Result

Case Conversion Functions

Convert case for character strings

LOWER(SQL Course)

UPPER(SQL Course)

INITCAP(SQL Course)

sql course

SQL COURSE

Sql Course


39/174



Hint

Explain the RPAD function, as this

function will be needed in a practice. Also,

LTRIM and RTRIM are replaced by one

function TRIM, in Oracle8i.



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Hint

Explain the syntax of the ROUND

function.

ROUND(n, [,m])

The ROUND function returns n rounded

to m places right of the decimal point; ifm

is omitted, to 0 places. m can be negative

to round off digits left of the decimal

point. m must be an integer.



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HintExplain the syntax of the TRUNC

function.

TRUNC(n, [,m])

The TRUNC function returns n truncated

to m decimal places; ifm is omitted, to 0

places. m can be negative to truncate

(make zero) m digits left of the decimal

point.



8.0/815/server.815/a67779/


CONCAT(Good, String)

SUBSTR(String,1,3)

LENGTH(String)

INSTR(String, r)

LPAD(sal,10,*)

GoodString

Str

6

3

******5000

Function Result

Character Manipulation Functions

Manipulate character strings

Using the ROUND Function

SQL> SELECT ROUND(45.923,2), ROUND(45.923,0),

2 ROUND(45.923,-1)

3 FROM DUAL;

ROUND(45.923,2) ROUND(45.923,0) ROUND(45.923,-1)

--------------- -------------- -----------------45.92 46 50

SQL> SELECT TRUNC(45.923,2), TRUNC(45.923),

2 TRUNC(45.923,-1)

3 FROM DUAL;

TRUNC(45.923,2) TRUNC(45.923) TRUNC(45.923,-1)--------------- ------------- ---------------

45.92 45 40

Using the TRUNC Function


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.....................................................................................................................................................

Hint

Explain the syntax of the MOD function

MOD(n, m)

The MOD function returns the reminder of

m divided by n. Returns m ifn is 0.

Additional Example

SELECT MOD(11,4) Modulus

FROM DUAL;

Modulus

-----------

3

Hint

If you specify a date value without a timecomponent, the default time is 12:00:00

AM (midnight). If you specify a time

value without a date, the default date is the

first day of the current month.



8.0/815/server.815/a67779/

ch2.htm#3463

Additional ExampleSELECT ename,

ROUND((SYSDATE-HIREDATE)/

365,1) YEARS

FROM emp;

The above example returns the name and

the number of years of service for all

employees rounded to the first decimal

place.

Using the MOD Function

Calculate the remainder of the ratio ofsalary to commission for all employees

whose job title is salesman.

SQL> SELECT ename, sal, comm, MOD(sal, comm)

2 FROM emp

3 WHERE job = SALESMAN;

ENAME SAL COMM MOD(SAL,COMM)---------- --------- --------- -------------

MARTIN 1250 1400 1250 ALLEN 1600 300 100TURNER 1500 0 1500

WARD 1250 500 250

Working with Dates

Oracle stores dates in an internalnumeric format: century, year, month,day, hours, minutes, seconds.

The default date format is DD-MON-YY.

SYSDATE is a function returning dateand time.

DUAL is a dummy table used to viewSYSDATE.

Using Arithmetic Operatorswith Dates

SQL> SELECT ename, (SYSDATE-hiredate)/7 WEEKS

2 FROM emp

3 WHERE deptno = 10;

ENAME WEEKS---------- ---------KING 830.93709CLARK 853.93709

MILLER 821.36566


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Hint

Explain that if you call a SQL function

with an argument of a datatype other thanthe datatype expected by the SQL

function, Oracle implicitly converts the

argument to the expected datatype before

performing the SQL function.



8.0/815/server.815/a67779/

ch2.htm#21067

Date Functions

Number of monthsbetween two dates

MONTHS_BETWEEN

ADD_MONTHS

NEXT_DAY

LAST_DAY

ROUND

TRUNC

Add calendar months todate

Next day of the datespecified

Last day of the month

Round date

Truncate date

Function Description

MONTHS_BETWEEN ('01-SEP-95','11-JAN-94')

Using Date Functions

ADD_MONTHS ('11-JAN-94',6)

NEXT_DAY ('01-SEP-95','FRIDAY')

LAST_DAY('01-SEP-95')

19.6774194

'11-JUL-94'

'08-SEP-95'

'30-SEP-95'

Conversion Functions

Implicit datatypeconversion

Explicit datatypeconversion

Datatypeconversion


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.....................................................................................................................................................



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ch2.htm#21067

Hint

Explain that you can use date format

models in a TO_CHAR function to do the

following: In the TO_CHAR function to translate

a DATE value that is in a format other

than the default date format

In the TO_DATE function to translate

a character value that is in a format

other than the default date format



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ch2.htm#35921



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Explicit Datatype Conversion

NUMBER CHARACTER

TO_CHAR

TO_NUMBER

DATE

TO_CHAR

TO_DATE

TO_CHAR Function with Dates

The format model:

Must be enclosed in single quotation marksand is case sensitive

Can include any valid date format element

Has an fmelement to remove paddedblanks or suppress leading zeros

Is separated from the date value by acomma

TO_CHAR(date, fmt)TO_CHAR(date, fmt)

Using TO_CHAR Functionwith Numbers

SQL> SELECT TO_CHAR(sal,$99,999) SALARY

2 FROM emp

3 WHERE ename = SCOTT;

SALARY--------

$3,000


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information in the class. The RR date

format element is similar to the YY dateformat element, but it provides additional

flexibility for storing date values in other

centuries. The RR date format element

allows you to store 21st century dates in

the 20th century by specifying only the

last two digits of the year. It will also

allow you to store 20th century dates in

the 21st century in the same way if

necessary.

If you use the TO_DATE function with

the YY date format element, the date

value returned is always in the current

century. If you use the RR date format

element instead, the century of the return

value varies according to the specified

two-digit year and the last two digits of the

current year



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ch2.htm#21067

TO_NUMBER and TO_DATEFunctions

Convert a character string to a number

format using the TO_NUMBER function

TO_NUMBER(char[, fmt])

Convert a character string to a dateformat using the TO_DATE function

TO_DATE(char[, fmt])TO_DATE(char[, fmt])

TO_NUMBER and TO_DATEFunctions

Convert a character string to a numberformat using the TO_NUMBER function

TO_NUMBER(char[, fmt])

Convert a character string to a dateformat using the TO_DATE function

TO_DATE(char[, fmt])TO_DATE(char[, fmt])


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.....................................................................................................................................................



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NVL Function

Converts null to an actual value

Datatypes that can be used are date,character, and number.

Datatypes must match

NVL(comm,0)

NVL(hiredate,01-JAN-97)

NVL(job,No Job Yet)


45/174



Additional Example

SELECT ename,

NVL(TO_CHAR(COMM),NOT

APPLICABLE)"COMMISSION"

FROM emp

WHERE deptno = 30;

ENAME COMMISSION

-------- ----------------

ALLEN 300

WARD 500

MARTIN 1400

BLAKE NOT APPLICABLE

TURNER 0

JAMES NOT APPLICABLE



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Hint

Explain that in a DECODE expression,

Oracle considers two nulls to be

equivalent. The maximum number of

components in the DECODE expression,

including expr, searches, results, and

default is 255.

Additional Reference:

SQL Language Reference Manual,

pp. 3 to 62

SQL> SELECT ename, sal, comm, (sal*12)+NVL(comm,0)

2 FROM emp;

Using the NVL Function

ENAME SAL COMM (SAL*12)+NVL(COMM,0)---------- --------- --------- --------------------

KING 5000 60000BLAKE 2850 34200CLARK 2450 29400JONES 2975 35700

MARTIN 1250 1400 16400 ALLEN 1600 300 19500...14 rows selected.

DECODE Function

Facilitates conditional inquiries by doingthe work of a CASE or IF-THEN-ELSEstatement

DECODE(col/expression, search1, result1

[, search2, result2,...,]

[, default])


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.....................................................................................................................................................

Lesson 4: Displaying Data from Multiple Tables



information in class. JOINS make it

possible to select data from more than one

table by means of a single statement.

The joining of tables is done in SQL by

specifying the tables to be joined in the

FROM clause of the SELECT statement.

When you join two tables a Cartesian

product is formed. The conditions for

selecting rows from the product are

determined by the predicates in the where

clause. All the subsequent WHERE,

GROUP BY, HAVING, and ORDER BY

clauses work on this product.

Additional Example

To get the details of all departments with

number of employees assigned to it (even

0 employees)

What Is a Join?

Use a join to query data from more thanone table.

Write the join condition in the WHEREclause.

Prefix the column name with the tablename when the same column nameappears in more than one table.

SELECT table1.column, table2.column

FROM table1, table2

WHERE table1.column1 = table2.column2;

Outer Joins

EMP DEPT

No employee in theOPERATIONS department

ENAME DEPTNO----- ------

KING 10BLAKE 30

CLARK 10

JONES 20

...

DEPTNO DNAME

------ ----------

10 ACCOUNTING30 SALES

10 ACCOUNTING20 RESEARCH

...40 OPERATIONS


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.....................................................................................................................................................Lesson 4: Displaying Data from Multiple Tables

SELECT d.deptno,d.dname,d.loc, count(empno) No of Employees

FROM d.dept, emp

WHERE emp.deptno(+) = d.deptno

GROUP BY d.deptno, d.dname,d.loc;

DEPTNO DNAME LOC No of Employees

------- ---------------- ---------- ---------------

10 ACCOUNTING NEW YORK 3

20 RESEARCH DALLAS 5

30 SALES CHICAGO 6

40 OPERATIONS BOSTON 0

Hint

Explain that if the same table is used more

than once in a FROM clause then to

remove conflicts and ambiguities table

aliases are used. They are also called asco-relation names or range variables.

Once aliases are used, table names cannot

be used in further clauses.

Self Joins

EMP (WORKER) EMP (MANAGER)

MGR in the WORKER table is equal to EMPNO in theMANAGER table

EMPNO ENAME MGR----- ------ ----

7839 KING

7698 BLAKE 78397782 CLARK 7839

7566 JONES 7839

7654 MARTIN 76987499 ALLEN 7698

EMPNO ENAME----- --------

7839 KING7839 KING

7839 KING

7698 BLAKE7698 BLAKE


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.....................................................................................................................................................

Lesson 5: Aggregating Data Using Group Functions

Hint

Explain that aggregate functions return a

single row based on groups of rows, rather

than on single rows.



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Hint

Highlight that all aggregate functions

except COUNT(*) and GROUPING

ignore nulls. You can use the NVL in the

argument to an aggregate function to

substitute a value for a null. If a query

with an aggregate function returns no rows

or only rows with nulls for the argument to

the aggregate function, the aggregate

function returns null.

What Are Group Functions?Group functions operate on sets of rows to give

one result per group.EMP

maximumsalary in

the EMP table

DEPTNO SAL--------- ---------

10 245010 500010 1300

20 80020 110020 300020 300020 297530 160030 285030 125030 95030 150030 1250

MAX(SAL)

---------

5000

Types of Group Functions

AVG

COUNT

MAX

MIN

STDDEV

SUM

VARIANCE

Group Functions and Null Values

Group functions ignore null values in thecolumn.

SQL> SELECT AVG(comm)

2 FROM emp;

AVG(COMM)

---------

550


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.....................................................................................................................................................Lesson 5: Aggregating Data Using Group Functions

Hint

Highlight that all aggregate functions

except COUNT(*) and GROUPING

ignore nulls. You can use the NVL in the

argument to an aggregate function tosubstitute a value for a null. If a query

with an aggregate function returns no rows

or only rows with nulls for the argument to

the aggregate function, the aggregate

function returns null.


If time permits, include that all the

SELECT statements we have used until

now have acted on data as if it is in a

single group. But the rows of data in some

of the tables can be thought of as being

part of different groups. For example, the

EMP table contains employees who are

clerks, sales representative, etc. If we want

to find the minimum salary of each group

of employees, then none of the clauses

that we have seen until now are of any use.

The GROUP BY clause is used here.

When a GROUP BY clause is used, each

row of the resulting table will represent a

group having same values in the columns

used for grouping.

Creating Groups of Data

EMP

average

salaryin EMPtable

for eachdepartment

2916.6667

2175

1566.6667

DEPTNO SAL--------- ---------

10 245010 500010 130020 80020 110020 300020 300020 2975

30 160030 285030 1250

30 95030 150030 1250

DEPTNO AVG(SAL)

------- ---------

10 2916.6667

20 2175

30 1566.6667


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.....................................................................................................................................................

Additional Example

SELECT job, max(sal)

FROM emp

GROUP BY job;

Hint

Highlight that the HAVING clause acts on

the resulting grouped table, from the

GROUP BY clause to remove the rowwhich does not satisfy the criteria in the

HAVIN

Documents

Instructor Guide for Introduction