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Chapter 1 Oracle9i: SQL 1

Chapter 1

Overview of Database Concepts


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Chapter Objectives Identify the purpose of a database

management system (DBMS)

Distinguish a field from a record and a

column from a row

Define the three types of relationships that

can exist between entities


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Chapter Objectives Identify the problem associated with many-

to-many relationships and the appropriate

solutions

Explain the purpose of normalization

Describe the role of a primary key

Identify partial dependency and transitive

dependency in the normalization process


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Chapter Objectives Explain the purpose of a foreign key

Determine how to link data in different

tables through the use of a common field

Explain the purpose of a structured query

language (SQL)


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Database Terminology Database logical structure to store

data

Database Management System

(DBMS) software used to create

and interact with the database


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Database Components Character

Field

Record

File


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Database Components -

Character Basic unit of data

Can be a letter, number, or special symbol


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Chapter 1 Oracle9i:

SQL 8

Database Components - Field A group of related characters

Represents an attribute or characteristic of

an entity

Corresponds to a column in the physical

database


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Chapter 1 Oracle9i:

SQL 9

Database Components - Record A collection of fields for one specific entity

Corresponds to a row in the physical

database


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Chapter 1 Oracle9i:

SQL 10

Database Components - File A group of records about the same type of

entity


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Chapter 1 Oracle9i:

SQL 11

Components Example


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Chapter 1 Oracle9i:

SQL 12

Review of Database Design Systems Development Life Cycle (SDLC)

Normalization


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Chapter 1 Oracle9i:

SQL 13

Systems Development Life Cycle

(SDLC) Systems investigation understanding the

problem

Systems analysis understanding the

solution

Systems design creating the logical and

physical components


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Chapter 1 Oracle9i:

SQL 14

Systems Development Life Cycle

(SDLC) Systems implementation placing

completed system into operation

Systems maintenance and review

evaluating the implemented system


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Chapter 1 Oracle9i:

SQL 15

Relationships

The following relationships can be

included in an E-R Model:

One-to-one

One-to-many

Many-to-many


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Chapter 1 Oracle9i:

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One-to-one Relationship Each occurrence of data in one entity is

represented by only one occurrence of data

in the other entity

Example: Each individual has just one

Employee id and each Employee id is

assigned to just one person


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Chapter 1 Oracle9i:

SQL 17

One-to-many Relationship Each occurrence of data in one entity can be

represented by many occurrences of the

data in the other entity

Example: Shashank ---- Employees


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Chapter 1 Oracle9i:

SQL 18

Many-to-many Relationship Data can have multiple occurrences in both

entities

Example: A student can take many classes

and each class is composed of many

students

Can not be included in the physical database


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Chapter 1 Oracle9i:

SQL 19

Normalization Determines required tables and columns for

each table

Multi-step process

Used to reduce or control data redundancy


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Chapter 1 Oracle9i:

SQL 20

Unnormalized DataContains repeating Hotels in the Oct_hotel

table


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Chapter 1 Oracle9i:

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First-Normal Form (1NF) Primary key is identified

Repeating groups are eliminated


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First-Normal Form (1NF)Oct_hotel_id is the primary key for Oct_hotel (Not null and Unique).


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Chapter 1 Oracle9i:

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Composite Primary Key More than one column is required to

uniquely identify a row

Can lead to partial dependency - a column

is only dependent on a portion of the

primary key


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Chapter 1 Oracle9i:

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Second-Normal Form (2NF) Partial dependency must be eliminated

Break the composite primary key intotwo parts, each part representing a

separate table


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Second-Normal Form (2NF)Oct_hotel table in 2NF


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Third-Normal Form (3NF)Partial and transitive dependency removed.


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Summary of Normalization Steps 1NF: eliminate repeating groups, identify

primary key

2NF: table is in 1NF and partial

dependencies eliminated

3NF: table is in 2NF and transitive

dependencies eliminated


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Linking Tables Once tables are normalized, make certain

tables are linked

Tables are linked through a common field

A common field is usually a primary key in

one table and a foreign key in the other

table


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Structured Query Language

(SQL) Data sublanguage

Used to:

Create or modify tables

Add data to tables

Edit data in tables

Retrieve data from tables


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Chapter 2

Basic SQL SELECT Statements Select * from oct_hotel;

Select * from dst_destination;

Select * from Top_destination;


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Chapter Objectives Distinguish between an RDBMS and an

ORDBMS

Identify keywords, mandatory clauses, and

optional clauses in a SELECT statement

Select and view all columns of a table

Select and view one column of a table


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Chapter Objectives Display multiple columns of a table

Use a column alias to clarify the contents of

a particular column

Perform basic arithmetic operations in the

SELECT clause


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Chapter Objectives Remove duplicate lists, using either the

DISTINCT or UNIQUE keyword

Combine fields, literals, and other data

Format output


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Relational Database Management

System (RDBMS)An RDBMS is the software program used to

create the database and it allows you to

enter, manipulate, and retrieve data


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Object Relational Database

Management System (ORDBMS)Same as an RDBMS except it can be used

to reference objects such as maps and object

fields


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SELECT Statement Syntax SELECT statements are used to retrieve

data from the database

Syntax gives the basic structure, or rules,

for a command


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SELECT Statement SyntaxOptional clauses and keywords are shown in

brackets


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SELECT Statement Syntax SELECT and FROM clauses are required

SELECT clause identifies column(s)

FROM clause identifies table(s)

Each clause begins with a keyword


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Selecting All Data in a TableSubstitute an asterisk for the column names in a

SELECT clause

Select * from oct_hotel;


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Selecting Column from a TableEnter column name in SELECT clause


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Operations Within the SELECT

Statement Column alias can be used for column

headings

Perform arithmetic operations

Suppress duplicates

Concatenate data


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Column Alias List after column heading

AS keyword is optional

Enclose in double quotation marks:

If it contains blank space(s)

If it contains special symbol(s)

To retain case


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Column Alias Example


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Arithmetic Operations Executed left to right

Multiplication and division are solved first

Addition and subtraction are solved last

Override order with parentheses


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Suppressing DuplicatesEnter DISTINCT or UNIQUE after

SELECT keyword

Select distinct hotel_nme from

oct_hotel;


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Concatenation Can combine data with string literal

Use concatenation operator, ||

Allows use of column alias


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Chapter 3

Restricting Rows and Sorting

Data


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Chapter Objectives

Use a WHERE clause to restrict the rows

returned by a query

Create a search condition using

mathematical comparison operators

Use the BETWEENAND comparison

operator to identify records within a rangeof values


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Chapter Objectives

Specify a list of values for a search

condition using the IN comparison operator

Search for patterns using the LIKE

comparison operator

Identify the purpose of the % and _

wildcard characters


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Chapter Objectives

Join multiple search conditions using the

appropriate logical operator

Perform searches for null values

Specify the order for the presentation of

query results, using ORDER BY, DESC,

ASC, and the SELECT clause


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WHERE Clause

Used to retrieve rows based on a stated

condition

Requires:

Column name

Comparison operator

Value or column for comparison

Case sensitive


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WHERE Clause Example

List WHERE clause after FROM clause

Enclose non-numeric data in single quotes


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Comparison Operators

Indicates how the data should relate to the

given search value


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Arithmetic Comparison

Operators


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Other Comparison Operators


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IN Operator

Match a value in a specified list

List must be in parentheses

Values separated by commas


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IN Operator Example


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LIKE Operator

Performs pattern searches

Used with wildcard characters

Underscore (_) for exactly one character in the

indicated position

Percent sign (%) to represent any number of

characters


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LIKE Operator Example


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Logical Operators

Used to combine conditions

Evaluated in order of NOT, AND, OR

NOT reverses meaning

AND both conditions must be TRUE

OR at least one condition must be TRUE


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AND Logical Operator Example


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Resolving Multiple Types of

Operators1. Arithmetic operators

2. Comparison operators

3. Logical operators


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Treatment of NULL Values

Absence of data

Requires use of IS NULL operator


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ORDER BY Clause

Presents data in sorted order

Ascending order is default

Use DESC keyword to override column

default

255 columns maximum


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Sort Sequence

In ascending order, values will be listed in

the following sequence:

Numeric values

Character values

NULL values

In descending order, sequence is reversed


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ORDER BY Example


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Chapter 4

Joining Multiple Tables


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Chapter Objectives

Create a Cartesian join

Create an equality join using the WHERE clause

Create an equality join using the JOIN keyword

Create a non-equality join using the WHERE

clause

Create a non-equality join using the JOINONapproach


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Chapter Objectives

Create a self-join

Distinguish an inner join from an outer join

Create an outer join using the WHERE clause

Create an outer join using the OUTER

keyword

Use set operators to combine the results ofmultiple queries

Join three or more tables


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Purpose of Joins

Joins are used to link tables and reconstruct

data in a relational database

Joins can be created through:

Conditions in a WHERE clause

Use of JOIN keywords in FROM clause


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Cartesian Join

Created by omitting joining condition in the

WHERE clause or through CROSS JOIN

keywords in the FROM clause Results in every possible row combination

(m * n)


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Cartesian Join Example:

Omitted Condition select * from oct_hotel, dst_destination;

select * from oct_hotel cross join

dst_destination;


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Equality Join

Links rows through equivalent data that

exists in both tables

Created by:

Creating equivalency condition in the WHERE

clause

Using NATURAL JOIN, JOINUSING, orJOINON keywords in the FROM clause


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Equality Join: WHERE Clause

Example


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Equality Join: NATURAL JOIN

Syntax: tablenameNATURAL JOIN tablename


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Equality Join: JOINUSING

Syntax: tablename JOIN tablenameUSING (columnname)


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Equality Join: JOINON

Syntax: tablename JOIN tablenameON condition


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JOIN Keyword Overview

Use NATURAL JOIN when tables have one

column in common

Use JOINUSING when tables have more thanone column in common

Use JOINON when a condition is needed to

specify a relationship other than equivalency

Using JOIN keyword frees the WHERE clause for

exclusive use in restricting rows


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Non-Equality Joins

In WHERE clause, use any comparison

operator other than equal sign

In FROM clause, use JOINON keywordswith non-equivalent condition


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Self-Joins

Used to link a table to itself

Requires use of column qualifier


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Self-Join: WHERE Clause

Example


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Outer Joins

Use to include rows that do not have a

match in the other table

In WHERE clause, include outer joinoperator (+) next to table with missing rows

to add NULL rows

In FROM clause, use FULL, LEFT, orRIGHT with OUTER JOIN keywords


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Outer Join: WHERE Clause

Example


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Outer Join: OUTER JOIN

Keyword Exampleselect distinct(a.geoname_id),b.name from oct_hotel a

left outer join dst_destination b on

a.geoname_id=b.geoname_id;

select distinct(a.geoname_id),b.name from oct_hotel a

right outer join dst_destination b on


select distinct(a.geoname_id),b.name from oct_hotel a

full outer join dst_destination b on



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Set Operators

Used to combine the results of two or more

SELECT statements


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Set Operator Example

select geoname_id from (select geoname_id from dst_destination

where rownum


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Joining Three or More Tables

Same procedure as joining two tables

Will always results in one less join than the

number of tables being joined


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Joining Three or More Tables:

Example


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Chapter 5

Selected Single-Row Functions


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Chapter Objectives

Use the UPPER, LOWER, and INITCAP

functions to change the case of field values

and character strings Extract a substring using the SUBSTR

function

Determine the length of a character stringusing the LENGTH function


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Chapter Objectives

Use the LPAD and RPAD functions to pad a

string to a desired width

Use the LTRIM and RTRIM functions to removespecific characters strings

Round and truncate numeric data using the

ROUND and TRUNC functions

Calculate the number of months between twodates using the MONTHS_BETWEEN function


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Chapter Objectives

Identify and correct problems associated withcalculations involving null values using the NVLfunction

Display dates and numbers in a specific formatwith the TO_CHAR function

Determine the current date setting using theSYSDATE keyword

Nest functions inside other functions


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Terminology

Function predefined block of code that

accepts arguments

Single-row Function returns one row ofresults for each record processed

Multiple-row Function returns one result

per group of data processed


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Types of Functions


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Case Conversion Functions

Alter the case of data stored in a column or

character string


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LOWER Function

Used to convert characters to lower-case

letters


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UPPER Function

Used to convert characters to upper-case

letters


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INITCAP Function

Used to convert characters to mixed-case


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Character Manipulation

FunctionsManipulates data by extracting substrings,

counting number of characters, replacing

strings, etc.


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SUBSTR Function

Used to return a substring, or portion of a string


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LENGTH Function

Used to determine the number of characters in a

string


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LPAD and RPAD Functions

Used to pad, or fill in, a character string to a fixed

width


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LTRIM and RTRIM Functions

Used to remove a specific string of characters


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REPLACE Function

Substitutes a string with another specified string


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CONCAT Function

Used to concatenate two character strings


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Number Functions

Allows for manipulation of numeric data


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ROUND Function

Used to round numeric columns to a stated precision


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TRUNC Function

Used to truncate a numeric value to a specific position


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Date Functions

Used to perform date calculations or format

date values


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MONTHS_BETWEEN Function

Determines the number of months between

two dates


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ADD_MONTHS Function

Adds a specified number of months to a date


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NEXT_DAY Function

Determines the next occurrence of a

specified day of the week after a given date


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TO_DATE Function

Converts various date formats to the

internal format (DD-MON-YYYY) used by

Oracle9i


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Format Model Elements - Dates


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NVL Function

Substitutes a value for a NULL value

store_name Sales

Store A 300Store B NULL

Store C 150

SELECT SUM(NVL(Sales,100)) FROM Sales_Data;


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NVL2 Function

Allows different actions based on whether a value

is NULL


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TO_CHAR Function

Converts dates and numbers to a formatted

character string

Format Model Elements


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Format Model Elements

Time and Number


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Other Functions

NVL

NVL2

TO_CHAR

DECODE

SOUNDEX


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DECODE Function

Determines action based upon values in a list


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Nesting Functions

One function is used as an argument inside

another function

Must include all arguments for each function Inner function is resolved first, then outer function


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Chapter 6

Group Functions


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Chapter Objectives

Differentiate between single-row and multiple-row

functions

Use the SUM and AVG functions for numericcalculations

Use the COUNT function to return the number of

records containing non-NULL values

Use COUNT(*) to include records containingNULL values


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Chapter Objectives

Use the MIN and MAX functions with non-numeric fields

Determine when to use the GROUP BYclause to group data

Identify when the HAVING clause shouldbe used

List the order of precedence for evaluatingWHERE, GROUP BY, and HAVINGclauses


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Chapter Objectives

State the maximum depth for nesting group

functions

Nest a group function inside a single-rowfunction

Calculate the standard deviation and

variance of a set of data, using theSTDDEV and VARIANCE functions


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Group Functions

Return one result per group of rows

processed

Also called multiple-row and aggregatefunctions

All group functions ignore NULL values

except COUNT(*) Use DISTINCT to suppress duplicate values


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Group by Function

Calculates total amount stored in a numeric

column for a group of rows


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GROUP BY Clause

Used to group data

Must be used for individual column in the

SELECT clause with a group function Cannot reference column alias


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HAVING Clause

Having


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Order of Clause Evaluation

When included in the same SELECT

statement, evaluated in order of:

WHEREGROUP BY

HAVING


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Nesting Functions

Inner function resolved first

Maximum nesting depth: 2


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Chapter 7

Subqueries


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Chapter Objectives

Determine when it is appropriate to use a subquery

Identify which clauses can contain subqueries

Distinguish between an outer query and asubquery

Use a single-row subquery in a WHERE clause

Use a single-row subquery in a HAVING clause

Use a single-row subquery in a SELECT clause


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Chapter Objectives

Distinguish between single-row and multiple-row comparison operators

Use a multiple-row subquery in a WHEREclause

Use a multiple-row subquery in a HAVINGclause

Use a multiple-column subquery in a WHEREclause


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Chapter Objectives

Create an inline view using a multiple-

column subquery in a FROM clause

Compensate for NULL values in subqueries Distinguish between correlated and

uncorrelated subqueries

Nest a subquery inside another subquery


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Subquery

Used when query is based on unknown

value

A query nested inside another query Requires SELECT and FROM clauses

Must be enclosed in parentheses

Place on right side of comparison operator

f b i


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Types of Subqueries

Si l S b O


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Single-Row Subquery Operators

Can only return one result to outer query

Operators include =, >, =,

Single-Row Subquery


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Single Row Subquery

In WHERE ClauseUsed for comparison against individual data

Single-Row Subquery


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Single Row Subquery

In HAVING ClauseRequired when returned value is compared

to grouped data

Single-Row Subquery


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Single Row Subquery

In SELECT ClauseReplicates subquery value for each row displayed

M l i l R S b i


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Multiple-Row Subqueries

Return more than one row of results

Require use of IN, ANY, ALL, or EXISTS

operators

ANY d ALL O t


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ANY and ALL Operators

Combine with arithmetic operators

EXISTS O t


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EXISTS Operator

Determines whether condition exists in subquery

Multiple-Row Subquery


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p q y

In WHERE Clause

Multiple-Row Subquery


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p q y

In HAVING Clause

M lti l C l S b


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Multiple-Column Subquery

Returns more than one column in results

Can return more than one row

Column list on left side of operator must bein parentheses

Uses IN operator for WHERE and

HAVING clauses



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p q y

In FROM ClauseCreates temporary table



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p q y

In WHERE ClauseReturns multiple columns for evaluation

NULL V l


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NULL Values

When subquery might return NULL values, use NVL function

Uncorrelated S bq eries


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Uncorrelated Subqueries

Processing sequence:

Inner query executed first

Result passed to outer queryOuter query executed

Correlated Subqueries


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Correlated Subqueries

Inner query executed once for each row

processed by outer query

Inner query references row contained inouter query

Nested Subqueries


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Nested Subqueries

Maximum 255 subqueries if nested in

WHERE clause

No limit if nested in FROM clause Innermost subquery resolved first, then next

level, etc.

Nested Subquery Example


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Nested Subquery Example

Innermost resolved first (3), then second level (2),

then outer query (1)


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Chapter 8

Table Creation and Management

Chapter Objectives


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Chapter Objectives

Create a new table using the CREATE

TABLE command

Name a new column or table Use a subquery to create a new table

Add a column to an existing table

Modify the size of a column in an existingtable

Chapter Objectives


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Chapter Objectives

Drop a column from an existing table

Mark a column as unused, then delete it at a

later time Rename a table

Truncate a table

Drop a table

Database Table


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Database Table

A database object

Stores data for the database

Consists of columns and rows

Created and modified through Data

Definition Language (DDL) commands

Table and Column Names


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Table and Column Names

Maximum 30 characters - no blank spaces

Must begin with a letter

Can contain numbers, underscore (_), andnumber sign (#)

Must be unique

No reserved words allowed

Common Datatypes


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Common Datatypes

CREATE TABLE Command


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Column definition list must be enclosed in

parentheses

Datatype must be specified for each column Maximum of 1,000 columns



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Example

DESCRIBE Command


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DESCRIBE Command

Displays structure of specified table

Table Creation Through


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Subqueries Can use subquery to retrieve data from

existing table

Requires use of AS keyword New column names can be assigned

CREATE TABLEAS


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Command

CREATE TABLEAS


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Command Example

Modifying Existing Tables


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Modifying Existing Tables

Accomplished through ALTER TABLE

command

Use ADD clause to add a column Use MODIFY clause to change a column

Use DROP COLUMN to drop a column

ALTER TABLE Command


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Syntax

ALTER TABLEADD


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Command Example

ALTER TABLEMODIFY


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Command Example

Modification Guidelines


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Modification Guidelines

Column must be as wide as the data it

already contains

If a NUMBER column already containsdata, size cannot be decreased

Adding or changing default data does not

affect existing data

ALTER TABLEDROP


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COLUMN Command Can only reference one column per

execution

Deletion is permanent Cannot delete last remaining column in a

table

ALTER TABLESET


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UNUSED Command Once marked for deletion, column cannot

be restored

Storage space freed at later time

ALTER TABLEDROP


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UNUSED CommandFrees up storage space from columns

previously marked as unused

RENAME Command


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RENAME Command

Used to rename a table old name no longer valid

Truncating a Table


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TRUNCATE CommandRows are deleted - structure of table remains

DROP TABLE Command


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DROP TABLE Command

Table structure and contents are deleted


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Chapter Objectives


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p j

Explain the purpose of constraints in a table

Distinguish among PRIMARY KEY,

FOREIGN KEY, UNIQUE, CHECK, andNOT NULL constraints and the appropriate

use for each constraint

Distinguish between creating constraints at

the column level and table level

Chapter Objectives


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p j

Create PRIMARY KEY constraints for a

single column and a composite primary key

Create a FOREIGN KEY constraint Create a UNIQUE constraint

Create a CHECK constraint

Chapter Objectives


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p j

Create a NOT NULL constraint, using the

ALTER TABLEMODIFY command

Include constraints during table creation Use DISABLE and ENABLE commands

Use the DROP command

Constraints


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Rules used to enforce business rules,

practices, and policies

Rules used to ensure accuracy and integrityof data

Constraint Types


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yp

Naming Constraints


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g

Use optional CONSTRAINT keyword

during creation to assign a name

Let server name constraint using defaultformat SYS_Cn

Creating Constraints


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g

When:

During table creation

Modify existing table How:

Column level approach

Table level approach

General Syntax Column Level


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y

If a constraint is being created at the column

level, the constraint applies to the column

specified

General Syntax Table Level


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y

Approach can be used to create any

constraint type except NOT NULL

Required if constraint is based on multiplecolumns

Enforcement


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All constraints are enforced at the table

level

If a data value violates a constraint, theentire row is rejected

Adding Constraints to Existing


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Tables Added to existing table with ALTER

TABLE command

Add NOT NULL constraint using MODIFYclause

All other constraints added using ADD

clause

PRIMARY KEY Constraint


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Ensures that columns do not contain

duplicate or NULL values

Only one per table allowed

PRIMARY KEY Constraint for


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Composite KeyList column names within parentheses

separated by commas

FOREIGN KEY Constraint


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Requires a value to exist in referenced

column of other table

NULL values are allowed Enforces referential integrity

Maps to the PRIMARY KEY in parent table

FOREIGN KEY Constraint -


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Example


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UNIQUE Constraint


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No duplicates allowed in referenced column

NULL values are permitted

CHECK Constraint


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Updates and additions must meet specified

condition

NOT NULL Constraint


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Special CHECK constraint with IS NOT

NULL condition

Can only be created at column level Included in output of DESCRIBE command

Can only be added to existing table using

ALTER TABLEMODIFY command

NOT NULL Constraint Example


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Adding Constraints During Table


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Creation Column LevelInclude in column definition

Adding Constraints During Table


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Creation Table LevelInclude at end of column list

Viewing Constraints

USER CONSTRAINTS


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USER_CONSTRAINTS

Can display name, type, and condition of

CHECK constraints

Disabling/Enabling Constraints


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Use DISABLE or ENABLE clause of

ALTER TABLE command

Dropping a Constraint


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Constraints cannot be modified, must be

dropped and recreated

Actual syntax depends on type of constraintPRIMARY KEY - just list type of constraint

UNIQUE - include column name

All others - reference constraint name

ALTER TABLEDROP Syntax


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Chapter 10

Data Manipulation

Chapter Objectives


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Add a record to an existing table

Add a record containing a NULL value to

an existing table Use a subquery to copy records from an

existing table

Modify the existing rows within a table

Chapter Objectives


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Use substitution variables with an UPDATE

command

Issue the transaction control statementsCOMMIT and ROLLBACK

Differentiate between DDL, DML, and

transaction control commands

Chapter Objectives


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Delete records

Differentiate between a shared lock and an

exclusive lock Use the SELECTFOR UPDATE

command to create a shared lock

INSERT Command


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Used to add rows to existing tables

Identify table in the INSERT INTO clause

Specify data in the VALUES clause Can only add one row at a time to a table

INSERT Command Syntax


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Enclose non-numeric data in single quotes

If column list not provided, a value must be

assigned to each column in the table

INSERT Command Example


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Inserting NULL Value


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Omit column name from INSERT INTO

clause column list

Substitute two single quotation marks Use NULL keyword

Inserting Data from an Existing

Table


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ab e

Substitute subquery for VALUES clause

Modifying Existing Rows


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Modify rows using UPDATE command

Use UPDATE command to:

Add values to an existing rowChange existing values

UPDATE Command


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UPDATE clause identifies table

SET clause identifies column being changed

and new value Optional WHERE clause specifies row(s) to

be changed if omitted, will update all

rows

UPDATE Command Syntax


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UPDATE Command Example


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Substitution Variables


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Prompts user for value

Identified by ampersand (&) preceding

variable name Can be used to create interactive scripts

Substitution Variable Example


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Transaction Control


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Results of Data Manipulation Language

(DML) are not permanently updated to table

until explicit or implicit COMMIT occurs

Transaction control statements can:

Commit data through COMMIT command

Undo data changes through ROLLBACK

command

COMMIT


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Explicit COMMIT occurs by executing

COMMIT;

Implicit COMMIT occurs when DDLcommand is executed or user properly exits

system

Permanently updates table(s) and allows

other users to view changes

ROLLBACK


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Used to undo changes that have not been

committed

Occurs when:ROLLBACK; is executed

System restarts after crash

Deleting Rows


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DELETE command removes a row from a table

DELETE Command Omitting

WHERE Clause


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Omitting WHERE clause removes all rows

Table Locks


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Prevents users from changing same data or

objects

Two types:Shared prevents DML operations on portionof table

Exclusive locks table preventing other

exclusive or shared locks

Shared Lock


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Locks portion of table affected by DMLoperation

Implicitly occurs during UPDATE or

DELETE operations

Explicitly occurs through LOCK TABLEcommand with SHARE MODE option

Released when COMMIT (implicit orexplicit) or ROLLBACK occurs

Exclusive Lock


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Implicitly locks table for DDL operations -

CREATE or ALTER TABLE

Explicitly locked through LOCK TABLEcommand with EXCLUSIVE MODE option

Released after execution of DDL operation

or after user exits system

SELECTFOR UPDATE

Command


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Creates shared lock on retrieved portion of

table

Prevents one user from changing a rowwhile another user is selecting rows to be

changed

Released through implicit or explicit

commit

SELECTFOR UPDATE

Command Example


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Chapter 11

Views

Chapter Objectives


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Create a view, using CREATE VIEW

command or the CREATE OR REPLACE

VIEW command

Employ the FORCE and NO FORCE

options

State the purpose of the WITH CHECK

OPTION constraint

Chapter Objectives


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Explain the effect of the WITH READ

ONLY option

Update a record in a simple view

Re-create a view

Explain the implication of an expression in

a view for DML operations

Update a record in a complex view

Chapter Objectives


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Identify problems associated with adding

records to a complex view

Identify the key-preserved table underlying

a complex view

Drop a view

Explain inline views and the use of

ROWNUM to perform a TOP-N analysis

Views


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Permanent objects that store no data

Display data contained in other tables

Two purposes:Reduce complex query requirements for novice

users

Restrict users access to sensitive data

Types of Views


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CREATE VIEW Command


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Use OR REPLACE if view already exists

Use FORCE if underlying table does not

exist at time of creation Provide new column names if necessary

CREATE VIEW Options


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WITH CHECK OPTION constraint if

used, prevents data changes that will make

the data subsequently inaccessible to the

view

WITH READ ONLY prevents DML

operations

Simple View


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Only references one table no group

functions, GROUP BY clause, or

expressions

Simple View DML Operations


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Any DML operations are allowed through

simple views unless created with WITH

READ ONLY option

DML operations that violate constraints on

the underlying table are not allowed

Complex View


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May contain data from multiple tables or

data created with the GROUP BY clause,

functions, or expressions

Type of DML operations allowed depends

on various factors

DML Operations - Complex

Views with Expressions


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Values cannot be inserted into columns that

are based on arithmetic expressions

DML Operations Complex

Views from Multiple Tables


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DML operations can not be performed on

non key-preserved tables, but they are

permitted on key-preserved tables

DML Operations Other

Complex Views


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No DML operations are permitted on

complex views based on DISTINCT,

ROWNUM, GROUP BY, or a function

Dropping a View


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Use DROP VIEW command

Inline View


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Temporary table created by using subquery

in FROM clause

Can only be referenced while the command

is being executed

Most common usage TOP-N Analysis

TOP-N Analysis


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ORDER BY included to identify top values: descending for highest values, ascending for lowest values

Extract data based on ROWNUM


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Chapter 12

Additional Database Objects

Chapter Objectives


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Define the purpose of a sequence and state

how it can be used by an organization

Explain why gaps may appear in the

integers generated by a sequence

Correctly use the CREATE SEQUENCE

command to create a sequence

Chapter Objectives


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Identify which options cannot be changedby the ALTER SEQUENCE command

Use NEXTVAL and CURRVAL in an

INSERT command Explain when Oracle9i will automatically

create an index

Create an index, using the CREATEINDEX command

Chapter Objectives


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Delete an index, using the DELETE INDEX

command

Create a PUBLIC synonym

Delete a PUBLIC synonym

Identify the contents of different versions of

views used to access the data dictionary,

based on the prefix of the view

Database Objects


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Anything that has a name and defined

structure

Includes:

Sequence generate sequential integers

Index quickly locate specific records

Synonym alias for other database objects

Sequences


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Used for internal control purposes by

providing sequential integers for auditing

Used to generate unique value for primary

key column no correlation with actual row

contents

CREATE SEQUENCE

Command


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Various intervals allowed Default: 1

Can specify starting number Default: 1

CREATE SEQUENCE

Command


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Can specify MINVALUE for decreasing

sequence, MAXVALUE for increasing

Numbers can be reused if CYCLE specified

ORDER clause for application cluster

environment

Use CACHE to pre-generate integers

Default: 20

CREATE SEQUENCE

Command Example


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Verifying Sequence Values


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Query USER_SEQUENCES data dictionary

view

Using Sequence Values

i


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NEXTVAL generates integer

CURRVAL contains last integer

generated by NEXTVAL

Altering Sequence Definitions

A S Q C d


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Use ALTER SEQUENCE command

START WITH value cannot be altered

drop sequence and re-create

Changes cannot make current integers

invalid

ALTER SEQUENCE Command

Example


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DROP SEQUENCE Command

P i l d ff d


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Previous values generated are not affected

by removing a sequence from a database

Indexes

S f l f d l d


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Stores frequently referenced value and row

ID (ROWID)

Can be based on one column, multiple

columns, functions, or expressions

Creating an Index

I li itl t d b PRIMARY KEY d


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Implicitly created by PRIMARY KEY and

UNIQUE constraints

Explicitly created by CREATE INDEX

command

CREATE INDEX Command

Example


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Verifying an Index

I d li t d i USER INDEXES i


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Indexes listed in USER_INDEXES view

Removing an Index

U DROP INDEX d


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Use DROP INDEX command

Synonyms

S t li f d t b


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Serve as permanent aliases for database

objects

Can be private or public

Private synonyms are only available to user

who created them

PUBLIC synonyms are available to all database

users

CREATE SYNONYM

Command Syntax


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CREATE SYNONYM

Command Example


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Deleting a SYNONYM

A private synonym can be deleted by owner


272/273


A private synonym can be deleted by owner

A PUBLIC synonym can only be deleted by

a user with DBA privileges

Data Dictionary

Stores information about database objects


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Stores information about database objects

Owned by user SYS

Cannot be directly accessed by users Displays contents through data dictionary

views

Documents

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