Lecture9: Data Manipulation in SQL , Advanced SQL queries · Data Manipulation in SQL , Advanced SQL queries Ref. Chapter5 1 s -pt. Prepared by L. Nouf Almujally & Aisha AlArfaj IS220

Lecture9: Data Manipulation in SQL , Advanced SQL

queries

Ref. Chapter5

1

Coll

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Com

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Prepared by L. Nouf Almujally & Aisha AlArfaj

I S220 / I S 422 : Dat abase Fundam ent a l s

The Process of Database Design

Real World Domain

Conceptual model (ERD)

Relational Data Model

Create schema

(DDL)

Load Data

(DML)

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Tables in the Examples

Customer(custNo, custName, custSt, custCity, age)

Product(prodNo, prodName, prodDes, price)

Orders(ordNo, ordDate, custNo, prodNo, quantity)

Where

custName, custSt, custCity, prodName, prodDes are strings

ordDate is date

Others are numbers

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Sample Data in Customer Table

custNo custName custSt custCity age

1 C1 Olaya St Jeddah 20

2 C2 Mains St Riyadh 30

3 C3 Mains Rd Riyadh 25

4 C4 Mains Rd Dammam

5 C5 Mains Rd Riyadh

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Sample Data in Product Table

prodNo prodName prodDes price

100 P0 Food 100

101 P1 healthy food 100

102 P2 200

103 P3 self_raising

flour,80%wheat

300

104 P4 network 80x 300

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Sample Data in Orders Table

ordNo ordDate custNo prodNo quantity

1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

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Aggregate Functions

• COUNT - returns the number of selected values

• SUM - returns the sum of selected (numeric) values

• AVG - returns the average of selected (numeric) values

• MIN - returns the minimum of selected values

• MAX - returns the maximum of selected values

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Use of COUNT(column_name)

• The COUNT(column_name) function returns the number of values (NULL values will not be counted) of the specified column

• Syntax

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SELECT COUNT(column_name)FROM table_name;

Use of COUNT(column_name)

Example 1: List the number of products in the product table

SELECT count(prodNo) FROM product;

Example 2: List the number of product descriptions in the product table

SELECT count(prodDes) FROM product;

Note: count(prodDes) does not count rows that have NULL value for prodDes.

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prodNo

prodName

prodDes price

100 P0 Food 100


102 P2 200

103 P3 self_raisingflour,80%wheat

300


COUNT(PRODNO)

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

5

COUNT(PRODDES)

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

4

Use of COUNT(*)

• The COUNT(*) function returns the number of records in a table (NULL values will be counted)

• Syntax

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SELECT COUNT(*)FROM table_name;

Use of COUNT (*)

Example 1: How many products are there in the product table?

SELECT count(*) FROM product;

Example 2: How many products are priced at 300?

SELECT count(*)

FROM product

WHERE price =300;

Note: count(*) also count rows that have NULL values

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prodNo

prodName

prodDes price

100 P0 Food 100


102 P2 200

103 P3 self_raisingflour,80%wheat

300


COUNT(*)

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

5

COUNT(*)

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

2

Use of COUNT(DISTINCT column_name)

• The COUNT(DISTINCT column_name) function returns the number of distinct values of the specified column:

• Syntax

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SELECT COUNT(DISTINCT column_name)FROM table_name;

Use of COUNT(DISTINCT column_name)

Example1: How many cities are the customers located in ?

SELECT count(distinct custCity) from customer;

Example 2: How many customers ordered products since 01/01/2003?

SELECT count(distinct custNo)

FROM orders

WHERE ordDate >= '01-jan-2003';

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ordNo ordDate cust

No

prodNo quantit

y

1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

COUNT(DISTINCT CUSTCITY)

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

3

COUNT(DISTINCT CUSTNO)

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

3

custNo custNam

e

custSt custCity age

1 C1 Olaya St Jeddah 20

2 C2 Mains St Riyadh 30

3 C3 Mains Rd Riyadh 25

4 C4 Mains Rd Dammam

5 C5 Mains Rd Riyadh

Use of SUM

The SUM() function returns the total sum of a numeric column.

• Syntax

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SELECT SUM(column_name)FROM table_name;

Use of SUM Example

Example 1: How many products pieces were ordered by customer 1?

SELECT SUM(quantity) FROM ordersWHERE custNo =1;

Example 2: How many orders were made by customer 1 and how many products pieces did he order?

SELECT count(ordNo), SUM(quantity) FROM ordersWHERE custNo =1;

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ordNo ordDate cust

No

prodNo quantit

y

1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

SUM(QUANTITY)

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

4

COUNT(ORDNO) SUM(QUANTITY)

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

3 4

Use of Avg

• The AVG() function returns the average value of a numeric column.

• Syntax

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SELECT AVG(column_name)FROM table_name;

Use of Min, Max

• The MIN() function returns the smallest value of the selected column.

• The MAX() function returns the largest value of the selected column.

• Syntax

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SELECT MIN(column_name), MAX (column_name)FROM table_name;

Example Use of AVG, MIN and MAX

Example: list the minimum, maximum and average price of all products.

SELECT MIN(price), MAX(price), AVG(price)

FROM product;

Note: if some product's price are NULLs, then SUM and AVG do not take those products into consideration.

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prodNo prodNam

e

prodDes price

100 P0 Food 100


102 P2 200

103 P3 self_raising

flour,80%wh

eat

300


MIN(PRICE) MAX(PRICE) AVG(PRICE)

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

100 300 200

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Advanced queries (GROUP BY)

• General Syntax of SELECT command

SELECT [DISTINCT]

{* | [columnExpression, ……. }

FROM TableName

[WHERE condition]

[GROUP BY columnList]

[HAVING condition]

[ORDER BY columnList]

• Order of the clauses cannot be changed.

• Only SELECT and FROM are mandatory

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The GROUP BY Statement

• The GROUP BY statement is used in conjunction with the aggregate functions to group the result-set by one or more columns.

• Syntax

SELECT column_name, aggregate_function(column_name)FROM table_name

WHERE condition GROUP BY column_name;

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Use of GROUP BY

• Use GROUP BY clause to get sub-totals.

• SELECT and GROUP BY closely integrated: each item in SELECTlist must be single-valued per group, and SELECT clause mayonly contain:

• Column names in the group by clause

• Aggregate functions

• Constants

• Expression involving combinations of the above

• If WHERE is used with GROUP BY, WHERE is applied first, thengroups are formed from rows satisfying condition.

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Example 1 ( use of group by )

• Orders

• find the total (total order) of each customer.

use the GROUP BY statement to group the customers.

SELECT Customer, SUM(OrderPrice)

FROM OrdersGROUP BY Customer;

O_Id OrderDate OrderPrice Customer

1 2008/11/12 1000 Nora

2 2008/10/23 1600 Sara

3 2008/09/02 700 Nora

4 2008/09/03 300 Nora

5 2008/08/30 2000 Yara

6 2008/10/04 100 Sara

Nora

Sara

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Example 1

• The result ( output ):

what happens if we omit the GROUP BY statement

SELECT Customer,SUM(OrderPrice) FROM Orders;

The result

Customer SUM(OrderPrice)

Nora 2000

Sara 1700

Yara 2000

Customer SUM(OrderPrice)

Nora 5700

Sara 5700

Nora 5700

Nora 5700

Yara 5700

Sara 5700

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Example 2

• List the quantity of each product ordered during Jan 2003.

SELECT prodNo, sum(quantity)

FROM orders

WHERE ordDate>='01-jan-2003' AND ordDate<'01-Feb-2003'

GROUP BY prodNo;


1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

PRODNO SUM(QUANTITY)

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

100 4

102 1

101 2

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Example 3

• return the minimum and maximum salaries for each department in the employees table

SELECT deptNumber, MIN(salary), MAX (salary)

FROM employees

GROUP BY deptNumber

ORDER BY deptNumber;

Employee No. First Name Last Name Dept Number Salary

E1 Mandy Smith D1 50000

E2 Daniel Hodges D2 45000

E3 Shaskia Ramanthan D2 58000

E4 Graham Burke D1 44000

E5 Annie Nguyen D1 60000D1

D2

DEPTNUMBER MIN(SALARY) MAX(SALARY)

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

D1 44000 60000

D2 45000 58000

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SELECT count(*)FROM EMPLOYEE;

Example 1 : no grouping






E5 Annie Nguyen D1 60000

Without group by COUNT(*) returns the number of rows in the table

COUNT(*)

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

5

Example 4

Grouping Output from Queries

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DEPTNUMBER COUNT(*)

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

D1 3

D2 2







Example 2 : group by

SELECT deptNumber, count(*)FROM EMPLOYEE

GROUP BY deptNumberORDER BY deptNumber;

Grouping Output from Queries

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Use of HAVING

• HAVING clause is designed for use with GROUP BY to restrict groups that appear in final result table.

• Similar to WHERE, but WHERE filters individual rows whereasHAVING filters groups.

• Column names in HAVING clause must also appear in theGROUP BY list or be contained within an aggregate function.

• SYNTAX

SELECT column_name, aggregate_function(column_name)FROM table_name

WHERE column_name operator valueGROUP BY column_name

HAVING aggregate_function(column_name) operator value ;

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EXAMPLE 1

• find if any of the customers have a total order of less than 2000

SELECT Customer,SUM(OrderPrice)

FROM OrdersGROUP BY Customer

HAVING SUM(OrderPrice)<2000;

- Without Having


1 2008/11/12 1000 Nora

2 2008/10/23 1600 Sara

3 2008/09/02 700 Nora

4 2008/09/03 300 Nora

5 2008/08/30 2000 Yara

6 2008/10/04 100 Sara

CUSTOMER SUM(ORDERPRICE)

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

SARA 1700


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

NORA 2000

SARA 1700

YARA 2000

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Example 2

• find if the customers “Nora" or “Yara" have a total order of more than 1500

SELECT Customer,SUM(OrderPrice)

FROM OrdersWHERE Customer=‘Nora' OR Customer=‘Yara'

GROUP BY CustomerHAVING SUM(OrderPrice)>1500 ;


1 2008/11/12 1000 Nora

2 2008/10/23 1600 Sara

3 2008/09/02 700 Nora

4 2008/09/03 300 Nora

5 2008/08/30 2000 Yara

6 2008/10/04 100 Sara


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

NORA 2000

YARA 2000

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Example 3

• List the product number and the quantity ordered for each product which has a total quantity of more than 2 during Jan 2003.

SELECT prodNo, sum(quantity)

FROM orders

WHERE ordDate>='01-jan-2003' AND ordDate<'01-Feb-2003'

GROUP BY prodNo

HAVING sum(quantity)>2;


1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

100= 4

101=2

102 = 1

PRODNO SUM(QUANTITY)

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

100 4

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Example 4• List the department number and the total number of employee in that

department for each department that has more than two employees

SELECT deptNumber, count(*)

FROM EMPLOYEE

GROUP BY deptNumber

HAVING count(*)>2

ORDER BY deptNumber;

DEPTNUMBER COUNT(*)

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

D1 3

DEPTNUMBER COUNT(*)

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

D1 3

D2 2







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Inserting Data Using Queries

• You can insert the result of a query into a table

For example, if you have a table Product_Expensive which has the same structure as Product, then you can use

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SQL> insert into Product_Expensive

select *

from product

where price>=200;

3 rows created.

PRODNO PRODNAME PRODDES PRICE

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

102 P2 200

103 P3 self_raising flour,80%wheat 300


SQL data loader*

• For a table containing a large data set, INSERT command is not efficient to populate the table

• Oracle provides a data loader utility SQLLOADER which can be used to load data

• The data can be loaded from any text file and inserted into the database.

• table must be created first

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SQL data loader*

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Discard file : contains

records that were not

inserted into any table in

the database

Bad file : contains

records that were

rejected because the

input format is invalid.

Log file : records of

successful SQL*Loader

execution

Database : where the

data is loaded

output

Datafiles:

Contains Data

Records

Control file :

text file tells

SQL*Loader

where to insert

the data.

input

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References

• “Database Systems: A Practical Approach to Design, Implementation and Management.” Thomas Connolly, Carolyn Begg. 5th Edition, Addison-Wesley, 2009.

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Documents

Lecture9: Data Manipulation in SQL , Advanced SQL queries · Data Manipulation in SQL , Advanced SQL queries Ref. Chapter5 1 s -pt. Prepared by L. Nouf Almujally & Aisha AlArfaj IS220