SQL (Structured Query Language)

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SQL

(

STRUCTURED QUERY

LANGUAGE

)



is a database computer language

designed for the retrieval and

management of data in :



relational database management systems

(RDBMS),



database schema creation and

modifcation, and

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 SQL is a standard interactive and programming

language for querying and modifying data and managing databases.

 Although SQL is both an ANSI and an ISO standard,

many database products support SQL with

proprietary extensions to the standard language.

 The core of SQL is formed by a command language

that allows the retrieval, insertion, updating, and deletion of data, and performing management and administrative functions.

 SQL also includes a Call Level Interface (SQL/CLI)

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 The frst version of SQL was developed at IBM by

Donald D. Chamberlin and Raymond F. Boyce in the early 1970s.

 This version, initially called SEQUEL, was designed

to manipulate and retrieve data stored in IBM's original relational database product, System R.

 IBM patented their version of SQL in 1985, while

the SQL language was not formally standardized until 1986, by the American National Standards Institute (ANSI).

 Subsequent versions of the SQL standard have

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

Originally designed as a declarative query and

data manipulation language, variations of SQL

have been created by SQL database

management system (DBMS) vendors that add:

 procedural constructs,

 control-of-fow statements,  user-defned data types, and

 various other language extensions.



With the release of the SQL:1999 standard, many

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MYSQL



Is freely available as an open source

software.



Was created in 1990s by Michael

Widenius of TeX DataKonsult AB in

Sweden.



Is currently the world’s most popular

open source database.



Particularly suited for client server

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MYSQL



Organizations that used MySQL for their

database needs range from small

not-for-proft organizations to global manufacturing

companies, government agencies,

multinational news organizations, and

major Internet service providers.



MySQL also available for many diferent

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LANGUAGE ELEMENTS



The SQL language is sub-divided into several

language elements, including:

 Statements which may have a persistent efect on schemas and data, or which may control

transactions, program fow, connections, sessions, or diagnostics.

 Queries which retrieve data based on specifc criteria.

 Expressions which can produce either scalar

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LANGUAGE ELEMENTS

 Predicates which specify conditions that can be

evaluated to SQL three-valued logic (3VL) Boolean truth values and which are used to limit the efects of

statements and queries, or to change program fow.

 Clauses, which are in some cases optional, constituent

components of statements and queries.

 Whitespace is generally ignored in SQL statements and

queries, making it easier to format SQL code for readability.

 SQL statements also include the semicolon (";")

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QUERIES

 The most common operation in SQL databases is

the query, which is performed with the declarative SELECT keyword.

 SELECT retrieves data from a specifed table, or

multiple related tables, in a database.

 While often grouped with Data Manipulation

Language (DML) statements, the standard SELECT query is considered separate from SQL DML, as it has no persistent efects on the data stored in a database.

 Note that there are some platform-specifc

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QUERIES

 SQL queries allow the user to specify a description of

the desired result set, but it is left to the devices of the database management system (DBMS) to plan,

optimize, and perform the physical operations

necessary to produce that result set in as efcient a manner as possible.

 An SQL query includes a list of columns to be included

in the fnal result immediately following the SELECT keyword.

 An asterisk ("*") can also be used as a "wildcard"

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SELECT IS THE MOST COMPLEX STATEMENT IN

SQL, WITH SEVERAL OPTIONAL KEYWORDS

AND CLAUSES, INCLUDING:



FROM clause

 which indicates the source table or tables from which

the data is to be retrieved.

 can include optional JOIN clauses to join related tables

to one another based on user-specifed criteria.



WHERE clause

 includes a comparison predicate, which is used to

restrict the number of rows returned by the query.

 is applied before the GROUP BY clause.

 eliminates all rows from the result set where the

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SELECT IS THE MOST COMPLEX STATEMENT IN

AND CLAUSES, INCLUDING:

 GROUP BY clause

 is used to combine, or group, rows with related values

into elements of a smaller set of rows.

 is often used in conjunction with SQL aggregate functions

or to eliminate duplicate rows from a result set.

 HAVING clause

 includes a comparison predicate used to eliminate rows

after the GROUP BY clause is applied to the result set.

 Because it acts on the results of the GROUP BY clause,

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SELECT IS THE MOST COMPLEX STATEMENT IN

AND CLAUSES, INCLUDING:



ORDER BY clause

 is used to identify which columns are used to sort

the resulting data, and in which order they should be sorted (options are ascending or descending).

 The order of rows returned by an SQL query is

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DATA TYPES

DATA

TYPE DESCRIPTION

Char (n) Stores a character string n characters long. You use the char data type for columns that contain letters and special characters and for columns containing numbers that will not be used in any calculations. For example, the REP_NUM and CUSTOMER_NUM columns are both assigned the char data type.

Varchar (n) An alternative to char that stores a character string up to n characters long. Unlike char, all that is stored is the actual character string. If a character string 20 characters long is stored in a char (30) column, it will occupy 30 characters (20 characters + 10 blank spaces). If it is

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DATA TYPES

DATA

Date Stores date data. In MySQL, dates are enclosed in single quotation marks and have the form yyyy-mm-dd (for example, ‘2007-10-15’ is October 15, 2007).

Decimal (p,

q) Stores a decimal number p digits long with q of these digits being decimal places to the right of the decimal point. For example the data type decimal (5, 2) represents a number with three places to the left and two places to the right of the decimal (for example, 100.00). You can use the contents of the decimal columns in

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DATA TYPES

DATA

Int Stores integers, which are numbers without a decimal part. The valid range is -2147483648 to 2147483647. You can use the content of int columns in calculation. If you follow the word int into auto_increment, you create a column for which MySQL will automatically generate a new sequence number each time you add a new row.

Smallint Stores integers, but uses less space than the int data type. The valid range is -32768 to 32767. Smallint is a better choice than int

when you are certain that the column will store numbers within the indicated range. You can use the contents of smallint columns in

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SHOW DATABASE



mysql> SHOW

DATABASES;



Use the SHOW

statement to fnd out

what databases

currently exist on the

server

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CREATE DATABASE



mysql> CREATE

DATABASE newdb;

Create statement

Database name

The new

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USE DATABASE



mysql> USE newdb



Creating a database

does not select it for

use; you must do that

explicitly.



Note that USE, like

QUIT, does not require

a semicolon.



The USE statement is

special in another

way, too: it must be

given on a single line.

SQL command

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SHOW TABLES



mysql> SHOW

TABLES;



To create one or

more tables in the

current database,

you can use CREATE

TABLE statement.

It indicates that there is no table in the database.

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CREATE TABLE



mysql> CREATE

TABLE



Use a CREATE TABLE

statement to specify

the layout of your

table.



In this case, table

pelajar

will have 4

attributes.

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

If you want to fnd out about the

structure of a table, the DESCRIBE

command is useful; it displays

information about each of a table's

columns

DESCRIBE

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 ALTER TABLE is use to modify an existing column  It is consists of ADD, MODIFY and DROP column  ALTER TABLE statement:

ADD column

MODIFY column

DROP column

ALTER TABLE table

ADD (column datatype [DEFAULT expr][column datatype]….);

MODIFY (column datatype [DEFAULT expr][column datatype]….);

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 Example

 Table before add new column

 Execute ALTER TABLE statement to ADD:

 Table after execute  the ALTER TABLE  statement to ADD

ename hiredate

JAMES 03-FEB-97

SMITH 20-MAC-90

ADAMS 11-JUL-99

ALTER TABLE emp

ADD (job VARCHAR(9));

ename hiredate job

JAMES 03-FEB-97 PROGRAMMER

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 Example

 Table before MODIFY a column

 Execute ALTER TABLE statement to MODIFY:

 Table after execute  the ALTER TABLE  statement to

 MODIFY

ename job hiredate

JAMES PROGRAMMER 03-FEB-97

SMITH MANAGER 20-MAC-90

ADAMS CLERK 11-JUL-99

ename job hiredate

JAM PROGRAMMER 03-FEB-97

SMI MANAGER 20-MAC-90 ADA CLERK 11-JUL-99

LIN ACCOUNTANT 05-SEP-09 ALTER TABLE emp

MODIFY (ename VARCHAR(3));

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 Example

 Table before DROP column

 Execute ALTER TABLE statement to DROP:

 Table after execute  the ALTER TABLE  statement to DROP:

ename job hiredate

JAMES PROGRAMMER 03-FEB-97

SMITH MANAGER 20-MAC-90

ADAMS CLERK 11-JUL-99

ename hiredate

JAMES 03-FEB-97

SMITH 20-MAC-90 ADAMS 11-JUL-99

LINA 05-SEP-09 ALTER TABLE emp

DROP COLUMN job;

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Basic Structures in Query

Design

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 SELECT  to query data in the database

 INSERT  to insert data into a table

 UPDATE  to update data in a table

 DELETE  to delete data from a table

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 Purpose  to retrieve and display data from one or more database

tables.

 It is an extremely powerful command capable of performing the

equivalentof the relational algebra’s Selection, Projection and Join operations in a single statement.

 It is most frequently used SQL command.  Basic select statement:

 SELECT identifes what columns  FROM identifes which table

SELECT [DISTINCT] {*, column,…} FROM table;

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 Select all columns

 Select specifc columns

Deptno Dname Loc

10 Accounting New York

20 Research Dallas 30 Sales Chicago SELECT * FROM dept;

Outpu t

Deptno Loc

10 New York

20 Dallas 30 Chicago SELECT Deptno, loc FROM dept;Outpu_t

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SELECT [DISTINCT] {*, column,…} FROM table

WHERE condition(s); •_Using_WHERE_clause.

•_{It is used to restrict or limiting the rows selected}

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 Using where clause

 Select specifc columns

ename job deptno

JAMES CLERK 30

SMITH CLERK 20 ADAMS CLERK 10 SELECT ename, job, deptno

FROM dept

WHERE job = ‘CLERK’

Outpu t

Deptno Loc

10 New York SELECT Deptno, loc

FROM dept

WHERE loc = ‘New York’;

Outpu t

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 Using BETWEEN operator to display rows based on a range

of values

ename sal

JAMES 14252

SMITH 10000 ADAMS 12000 SELECT ename, sal

FROM emp

WHERE sal BETWEEN 10000 AND 15000;

Outpu t

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UPDATE

UPDATE item

SET Quantity =10,UnitPrice =1800.00

WHERE ItemNo = ‘123’;

In this statement , only one row will be

updated since the condition is specifed

in the WHERE clause, if the WHERE

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DELETE



To remove one or more rows from a

table. For example , to delete the

ItemNo = ‘123’.

DELETE

FROM item

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

The syntax for inserting data into a

table one row at a time is as follows:

INSERT INTO "table_name"

("column1", "column2", ...)

VALUES ("value1", "value2", ...)

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ASSUMING THAT WE HAVE A TABLE THAT HAS THE

FOLLOWING STRUCTURE :

TABLE STORE_INFORMATION RESULT :

Column Name Data Type

store_name char(50)

Sales float

Date datetime

INSERT INTO

Store_Information (store_name, Sales, Date)

VALUES (‘Ipoh', 900, 'Jan-10-1999')

store_name Sales Date

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

The second type of

INSERT INTO

allows

us to insert multiple rows into a table.



Unlike the previous example, we now use

a

SELECT

statement to specify the data

that we want to insert into the table.



The syntax is as follows:

INSERT INTO "table1" ("column1", "column2", ...) SELECT "column3", "column4", ...

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BEFORE USING INSERT INTO COMMAND

TABLE SALES_INFORMATION TABLE STORE_INFORMATION

store_na

me Branch Sales Date

Alor Setar Kedah 350 Mac- 4-1997 Butterwor

th Penang 500 Sep- 17-1997 Sepang Selang

or 675 Feb- 20-1998 Nilai Ng Sembil an 890 Mei- 15-1998 store_na

me Sales Date

Ipoh 900 Jan-10-1999

Table

Sales_Information

Table

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INSERT INTO Store_Information (store_name, Sales, Date) SELECT store_name, Sales, Date

FROM Sales_Information WHERE Year(Date) = 1998

AFTER USING INSERT INTO

COMMAND

store_n

ame Branch Sales Date

Alor

Setar Kedah 350 Mac- 4-1997 Butterwo

rth Penang 500 Sep- 17-1997 Sepang Selango

r 675 Feb- 20-1998 Nilai Ng Sembila n 890 Mei- 15-1998 store_na

me Sales Date

Ipoh 900 Jan-10-1999 Sepang 675

Feb-20-1998 Nilai 890

Mei-15-1998

New information that been added to the table

Table

Sales_Information

Table

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CREATE VIEW



Views can be considered as virtual tables.



Generally speaking, a table has a set of

defnition, and it physically stores the data.



A view also has a set of defnitions, which

is build on top of table(s) or other view(s),

and it does not physically store the data.



The syntax for creating a view is as follows:

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WE HAVE THE FOLLOWING TABLE

TABLE CUSTOMER

WE WANT TO CREATE A VIEW CALLED V_CUSTOMER THAT CONTAINS ONLY THE

FIRST_NAME, LAST_NAME, AND COUNTRY COLUMNS FROM THIS TABLE , WE WOULD TYPE IN,

CREATE VIEW V_Customer AS SELECT First_Name, Last_Name, Country FROM Customer

Column Name Data Type

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NOW WE HAVE A VIEW CALLED V_CUSTOMER WITH THE FOLLOWING STRUCTURE:



View

V_Customer

(First_Name

char(50),

Last_Name

char(50),

Country char(25))

Column Name Data Type

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WE CAN ALSO USE A VIEW TO APPLY JOINS TO TWO TABLES. IN THIS CASE, USERS ONLY SEE ONE VIEW RATHER THAN TWO TABLES, AND THE SQL

STATEMENT USERS NEED TO ISSUE BECOMES MUCH SIMPLER. LET'S SAY WE HAVE THE FOLLOWING TWO TABLES

TABLE STORE_INFORMATION TABLE GEOGRAPHY

store_name Sales Date

Los Angeles $1500 Jan-05-1999 San Diego $250 Jan-07-1999 Los Angeles $300 Jan-08-1999 Boston $700 Jan-08-1999

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WE WANT TO BUILD A VIEW THAT HAS SALES BY REGION INFORMATION



CREATE VIEW V_REGION_SALES

AS SELECT A1.region_name REGION,

SUM(A2.Sales) SALES

FROM Geography A1, Store_Information A2

WHERE A1.store_name = A2.store_name

GROUP BY A1.region_name



This gives us a view,

V_REGION_SALES

,

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

SELECT * FROM V_REGION_SALES

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EXERCISES:

ACCORDING TO THE TABLE GIVEN, WRITE SQL QUERY FOR EACH OF THE FOLLOWING

QUESTIONS.

Column

Name Data Type

Reg_Num Char(12) Name Char(50) Year_Born Int(4)

1. Add a column called

“TelNum” to this table.

2. Change the column

name for “Reg_Num” to “RegistrationNum”.

3. Modify the data type

of “Year_Born” to date.

4. Delete the column

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•

NOT NULL

•

UNIQUE

•

PRIMARY KEY

•

FOREIGN KEY

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TABLE CONSTRAINT



You can place constraints to limit the

type of data that can go into a table.



Such constraints can be specifed when

the table when the table is frst created

via the CREATE TABLE statement, or

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1)

NOT NULL



By default, a column can hold NULL.



If you not want to allow NULL value in a

column, you will want to place a

constraint on this column specifying

that NULL is now not an allowable

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Columns "SID" and "Last_Name" cannot include NULL, while

"First_Name" can include NULL.

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2) UNIQUE



The UNIQUE constraint ensures that all

values in a column are distinct.

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RESULT :

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3) PRIMARY KEY

 A primary key is used to uniquely identify each row in a table.

 It can either be part of the actual record itself , or it can be an artifcial feld.

 A primary key can consist of one or more felds on a table.

 When multiple felds are used as a primary key, they are called a composite key.

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EXAMPLE :



CREATE TABLE Customer

(SID integer,

Last_Name varchar(30),

First_Name varchar(30),

PRIMARY KEY (SID));



ALTER TABLE Customer ADD PRIMARY KEY

(SID);

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RESULT :

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4)

FOREIGN KEY



A foreign key is a feld (or felds) that

points to the primary key of another

table.



The purpose of the foreign key is to

ensure referential integrity of the data.



In other words, only values that are

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TABLE CUSTOMER TABLE ORDER

Column name Characteristic

SID Primary key First_Name

Last_Name

Column name Characteristic

Order_ID Primary key Order_Date

Customer_SID Foreign key Amount

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 CREATE TABLE ORDERS

(Order_ID integer, Order_Date date,

Customer_SID integer, Amount double,

Primary Key (Order_ID),

Foreign Key (Customer_SID) references CUSTOMER(SID));

 ALTER TABLE ORDERS

ADD FOREIGN KEY (customer_sid) REFERENCES CUSTOMER(SID);

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MANIPULATION DATA IN SQL

COMMANDS

•SORT BY ROW

•AND

•OR

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SORT BY ROW



The ORDER BY clause is used to sort

the rows.



Example :

Company OrderNumber

Sega 3412

ABC Shop 5678

W3Schools 6798

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EXAMPLE 1



To display the

company names in

alphabetical order:

SELECT Company,

OrderNumber FROM

OrdersORDER BY

Company

Compan

y OrderNum

ABC Shop 5678

Sega 3412

W3Schools 6798 W3Schools 2312

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EXAMPLE 2

 To display the

company names in alphabetical order

AND the OrderNumber in numerical order:

SELECT Company, OrderNumber FROM OrdersORDER BY Company, OrderNumber Compan

y OrderNum

ABC Shop 5678

Sega 3412

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EXAMPLE 3



To display the

company names in

reverse alphabetical

order:

SELECT Company,

OrderNumber FROM

OrdersORDER BY

Company DESC

Compan

y OrderNum

Sega 3412

ABC Shop 5678

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EXAMPLE 4

 To display the company names in reverse

alphabetical order AND the OrderNumber in

numerical order: SELECT Company, OrderNumber FROM OrdersORDER BY Company DESC, OrderNumber ASC Compan

y OrderNum

Sega 3412

ABC Shop 5678

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AND & OR

 AND and OR join two or more conditions in a

WHERE clause.

 The AND operator displays a row if ALL

conditions listed are true.

 The OR operator displays a row if ANY of the

conditions listed are true.

L_Name F_Name Address City

Hansen Ola Timoteivn 10 Sandnes

Svendson Tove Borgvn 23 Sandnes

Svendson Stephen Kaivn 18 Sandnes

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EXAMPLE 1



Use AND to display

each person with

the frst name equal

to "Tove", and the

last name equal to

"Svendson“:

SELECT * FROM Persons WHERE FirstName='Tove' AND LastName='Svendson'

L_Name F_Name Address City

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EXAMPLE 2



Use OR to display

each person with

the frst name equal

to "Tove", or the last

name equal to

"Svendson":

SELECT * FROM Persons WHERE frstname='Tove' OR lastname='Svendson'

L_Name F_Name Address City

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EXAMPLE 3



You can also

combine AND and

OR (use

parentheses to form

complex

expressions):

SELECT * FROM Persons WHERE

(FirstName='Tove' OR FirstName='Stephen') AND

LastName='Svendson'

L_Name F_Name Address City

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IN



The IN operator may be used if you

know the exact value you want to

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EXAMPLE 1



To display the

persons with

LastName equal to

"Hansen" or

"Pettersen", use the

following SQL:

SELECT * FROM Persons

WHERE LastName IN ('Hansen','Pettersen ')

L_Name F_Name Address City

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BETWEEN ... AND



The BETWEEN ... AND operator selects

a range of data between two values.



These values can be numbers, text, or

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EXAMPLE 1



To display the

persons

alphabetically

between (and

including) "Hansen"

and exclusive

"Pettersen“ :

WHERE LastName BETWEEN 'Hansen'

AND 'Pettersen'

L_Name F_Name Address City

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EXAMPLE 2



To display the

persons outside the

range used in the

previous example,

use the NOT

operator:

WHERE LastName NOT BETWEEN

'Hansen' AND 'Pettersen'

L_Name F_Name Address City

Pettersen Kari Storgt 20 Stavanger

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 Use the LIKE operator to perform wildcard searches of valid search string

values.

 Search conditions can contain either literal characters or numbers

- % denotes zero or many characters - _ denotes one characters

ename

LINA

SELECT ename FROM emp

WHERE ename LIKE ‘L%’;

Output

emp_code ename job

001 JAMES PROGRAMMER

003 ADAMS CLERK

002 SMITH MANAGER

004 LINA CLERK

Original table

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ename JAMES

ADAMS

SMITH

WHERE ename LIKE ‘_M%’;

Output

emp_code ename job

001 JAMES PROGRAMMER

003 ADAMS CLERK

002 SMITH MANAGER

004 LINA CLERK

Original table

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 You can use the ESCAPE identifer to search for “%” or “_”

ename

SMITH_WINE

WHERE ename LIKE ‘%\_%’ ESCAPE ‘\’;

Output

emp_code ename job

001 JAMES PROGRAMMER

003 ADAMS CLERK

002 SMITH_WINE MANAGER

004 LINA CLERK

Original table

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 Use the IN operator to test for

values in a list

SELECT ename, job FROM emp

WHERE emp_code IN (002,004);

Output

emp_code ename job

001 JAMES PROGRAMMER

003 ADAMS CLERK

002 SMITH_WINE MANAGER

004 LINA CLERK

Original table

ename job

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AVG

COUNT

MAX

MIN

SUM

VARIANCE

Types of Group Functions

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

COUNT

function is the simplest

function and very useful in counting the

number of records which are expected

to be returned by a SELECT statement.

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 Using AVG, MAX, MIN and SUM functions

AVG(sal) MAX(sal) MIN(sal) SUM(sal)

4150 8000 950 12450

SELECT AVG(sal), MAX(sal), MIN(sal), SUM(sal)

FROM emp;

sal 950 8000 3500

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 MAX function is used to fnd out the record with maximum value among a record set.

 To understand MAX function consider an

employee_tbl table which is having following records:

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NOW SUPPOSE BASED ON THE ABOVE TABLE YOU WANT TO FETCH MAXIMUM VALUE OF

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

You can use

MIN

Function alongwith

MAX

function to fnd out minimum

value as well.

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 AVG function is used to fnd out the average of a feld in various records.

 To understand AVG function consider an

employee_tbl table which is having following records:

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