SQL

Introduction

What is SQL?

• SQL stands for Structured Query Language

      you can access and manipulate(build) the database.

What Can SQL do?

SQL can execute queries against a database
SQL can retrieve data from a database
SQL can insert records in a database
SQL can update records in a database
SQL can delete records from a database
SQL can create new databases
SQL can create new tables in a database
SQL can create stored procedures in a database
SQL can create views in a database
SQL can set permissions on tables, procedures, and views

Database Tables

A database most often contains one or more tables. Each table is identified by a name (e.g. "Student" or "Employee"). Tables contain records (rows) with data.

>rows are also know as tuples.


 Student ID     Student name     contact     age
1                       Ash                    890          21
2                      Anny                  789           22
3                      Stain                   465           20
4                      Harry                  769            25
5                       Dev                    899            23

Some of The Most Important SQL Commands

SELECT - extracts data from a database
UPDATE - updates data in a database
DELETE - deletes data from a database
INSERT INTO - inserts new data into a database
CREATE DATABASE - creates a new database
ALTER DATABASE - modifies a database
CREATE TABLE - creates a new table
ALTER TABLE - modifies a table
DROP TABLE - deletes a table
CREATE INDEX - creates an index
DROP INDEX - deletes an index





 

The SQL SELECT Statement :

The SELECT statement is used to select data from a database.

SQL SELECT Syntax

 

SELECT column_name,column_name
FROM table_name;

and

 

SELECT * FROM table_name;

 

Example:

 

 SELECT * FROM Student;

 

The SQL SELECT DISTINCT Statement

In a table, a column may contain many duplicate values; and sometimes you only want to list the different (distinct) values.
 

 SELECT DISTINCT column_name,column_name
FROM table_name;

 

 

Example:

select distinct Student name from Student ;

The SQL WHERE Clause 

The WHERE clause is used to extract only those records that specifies the needs .

SQL WHERE Syntax

SELECT column_name,column_name
FROM table_name
WHERE column_name operator value;

 

Example 

 

SELECT * FROM Student
WHERE name='Ash';

 

Operators in The WHERE Clause

The following operators can be used in the WHERE clause:

Operator	Description
=	Equal
<>	Not equal.
>	Greater than
<	Less than
>=	Greater than or equal
<=	Less than or equal
BETWEEN	Between an inclusive range
LIKE	Search for a pattern
IN	To specify multiple possible values for a column