SQL is Structured Query Language, for storing, manipulating and retrieving data stored in relational database.Its a standard language for Relation Database System. All relational database management systems like MySQL, MS Access, Oracle, Sybase, Informix, postgres and SQL Server use SQL as standard database language.SQL is just a query language, it is not a database. To perform SQL queries, you need to install any database.

Uses of SQL

  • Allows users to access data in relational database management systems.
  • Allows users to describe the data.
  • Allows users to define the data in database and manipulate that data.

  • Allows to embed within other languages using SQL modules, libraries & pre-compilers.
  • Allows users to create and drop databases and tables.
  • Allows users to create view, stored procedure, functions in a database.
  • Allows users to set permissions on tables, procedures, and views

Following is a simple diagram showing SQL Architecture


Important SQL Commands

The standard SQL commands to interact with relational databases.The SQL Commands can be divided into three. ther are:

  • DDL – Data Definition Language
  • DML – Data Manipulation Language

  • DCL – Data Control Language

DDL – Data Definition Language

  • CREATE : For Creates a new table
  • ALTER :To Modifies an existing database object, such as a table.
  • DROP : To Deletes an entire table

DML – Data Manipulation Language

  • SELECT : Extract certain records from one or more tables
  • INSERT : Creates a record or insert the data into database.
  • UPDATE : Modifies records or update the data in a database
  • DELETE : Deletes records or delete the data from database.

DCL – Data Control Language

  • GRANT :Gives a privilege to user
  • REVOKE :Takes back privileges granted from user

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