Page 12 - Modular_V2.0_SQL_Flipbook

UNDERSTANDING SQL

SQL stands for Structured Query Language. It is pronounced as 'sequel'.

It is the standard language for managing relational databases and performing various operations on
the data in the tables. It would enable us to store, retrieve, and manipulate data in the form of tables.

SQL is a high-level interactive language that allows users to specify what is required to be done in
the form of queries. Unlike other high-level languages, you do not need to specify how the SQL
operations are implemented.
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The SQL was developed by IBM researchers Raymond Boyce and Donald Chamberlin in the 1970s.

Features of SQL

Some of the important features of SQL are as follows:

It has very high performance and efficiency.

It is easy to use.
It is available free of cost.

It supports standards based SQL.
It provides portability.

It provides high security.

DIFFERENT TYPES OF COMMANDS IN SQL

SQL commands or statements are the instructions given to database for performing an operation
like inserting a record, deleting a record,updating a record, etc. Such commands are categorised into:

Data Definition Language (DDL)

Data Manipulation Language (DML)
Data Control Language (DCL)

Transaction Control Language (TCL)

Data Definition Language (DDL)

A Data Definition Language or Data Description Language (DDL) is a standard for commands that
define database structures. DDL statements create, modify and remove database objects such as
tables, indexes and users. Common DDL statements are CREATE, ALTER, TRUNCATE, RENAME and

DROP.
Data Manipulation Language (DML)

A Data Manipulation language (DML) is a language that enables users to retrieve, update, insert

and delete data in a database. Common DML statements are SELECT, UPDATE, INSERT INTO and
DELETE.

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