Introduction to SQL

Introduction to SQL
 SQL (pronounced "ess-que-el") stands for
Structured Query Language.
 SQL is used to communicate with a database.
According to ANSI (American National Standards
Institute), it is the standard language for relational
database management systems. SQL statements
are used to perform tasks such as update data on a
database, or retrieve data from a database
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Introduction to SQL(CONT)
 However, the standard SQL commands such
as "Select", "Insert", "Update", "Delete",
"Create",
Query
 A query is an inquiry to the database for
information. A query is usually issued to the
database through an application interface or
via a command line prompt.
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Types of SQL Commands
 The main categories are
 DDL (Data Definition Language)
 DML (Data Manipulation Language)
 DQL (Data Query Language)
 DCL (Data Control Language)
 Data administration commands
 Transactional control commands
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Defining Database Structures
 Data Definition Language, DDL,
 Subset of sql statements.
 is the part of SQL that allows a database user to create and
restructure database objects, such as the creation or the
deletion of a table.
 Some of the most fundamental DDL commands discussed
during following hours include the following:
 CREATE TABLE
 ALTER TABLE (for add or drop cloumn’s in table )
 Change the datatype of cloumn’s
 DROP TABLE
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Manipulating Data
 Data Manipulation Language, DML, is the part
of SQL used to manipulate data within objects of
a relational database.
 Sometime It is also called read only quary.
 There are three basic DML commands:
 SELECT
 INSERT
 UPDATE
 DELETE
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Create Query
 Syntax
Create DATABASE database_name
Now we want to create database called
“mydb”. We use the following CREATE
DATABASE statement:
CREATE DATABASE my_db
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Selecting Data
 Though comprised of only one command, Data
Query Language (DQL) is the most concentrated
focus of SQL for modern relational database
users. The base command is as follows:
 SELECT
 This command, accompanied by many options
and clauses, is used to compose queries against a
relational database. Queries, from simple to
complex, from vague to specific, can be easily
created.
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Data Control Language
 Data control commands in SQL allow you to control
access to data within the database.
 These DCL commands are normally used to create
objects related to user access and also control the
distribution of privileges among users.
 Some data control commands are as follows:
 GRANT
 REVOKE
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Introduction to SQL

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