Relational Query Languages| Basic sql query language

BASIC SQL QUERY LANGUAGE

INTRODUCTION-

• SQL (Structured Query Language) is a special-purpose programming language designed for managing data held in a relational database management system (RDBMS).
• SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standards (ISO) in 1987. 

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

SQL LANGUAGES

1. Data Definition Language (DDL)

2. Data Manipulation Language (DML)

3. Data Control Language (DCL)

1) DATA DEFINITION LANGUAGE- The Data Definition Language (DDL) manages table and index structure.

COMMAND USED- CREATE, ALTER, DROP,RENAME

CREATE- creates an object (a table) in the database.

ALTER modifies the structure of an existing object in various ways, for  example, adding a column to an existing table or a constraint.

DROP deletes an object in the database, usually irretrievably, i.e., it cannot be rolled back.

RENAME rename scheme object

2) DATA MANIPULATION LANGUAGE- The Data Manipulation Language (DML) is the subset of SQL used to add, update,select and delete data.

COMMAND USED-INSERT, UPDATE, DELETE,SELECT

INSERT adds rows (formally tuples) to an existing table.

UPDATE modifies a set of existing table rows.

DELETE removes existing rows from a table.

SELECT Retrieve data from one or more table

3) DATA CONTROL LANGUAGE-The Data Control Language (DCL) authorizes users to access and manipulate data.          

COMMAND USED- GRANT, REVOKE, COMMENT

GRANT authorizes one or more users to perform an operation or a set of operations on an object.

REVOKE eliminates a grant, which may be the default grant.

COMMENT Adding the element into data dictionary