Overview of SQL


What is SQL?
  • SQL stands for the structured query language.
  • It is pronounced as S-Q-L or sometimes see-qwell.
  • In 1986 SQL became a standard of the American National Standards Institute(ANSI) , and of the International Organisation for Standardization(ISO) in 1987.
  • SQL is used for storing, manipulating , retrieving, and updating data stored in the relational database.
  • SQL is the standard language for Relational Database System. All  Relational Database Management System like MySQL, MS Access, Oracle, SQL Server use SQL as their standard database language.
  • SQL is also used to perform various operations on the records stored in the database such as creating tables, modifying tables, updating records, deleting records, etc.
  • SQL is just a query language, it is not a database.
  • SQL is based on relational algebra and tuple relational calculus.
Functions of SQL:-
  • It allows the user to describe the data.
  • Users can access data from the relational database management system.
  • With SQL, users can use English-like statements to query our database.
  • It allows the user to create and drop database and table.
  • It allows the user to create a view , stored procedure , function in a database.
SQL Syntax:- 
  • SQL uses some set of rules and regulations called syntax .
  • SQL is not case sensitive. Generally, the SQL keywords are written in uppercase.
  • You can perform most of the action in a database with SQL statements.
SQL STATEMENT:- 

SQL statements are started with any of the SQL commands/keywords like SELECT, INSERT, UPDATE, DELETE, ALTER ETC. and the statements end with a semicolon(;).

Example of SQL statement:-

 SELECT "column-name" FROM "table-name";

  • SELECT - extract data from the database.
  • UPDATE - updates data in the database.
  • DELETE - delete data from the database.
  • INSERT INTO - inserts new data into a database.
  • CREATE DATABASE - creates a new database.
  • ALTER DATABASE - modifies a database.
  • CREATE TABLE - creates a table.
  • DROP TABLE - deletes a table.
  • CREATE INDEX - it is used to create an index(search key).
  • DROP INDEX - it deletes an index.



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