introduction of sql

codelack_database

what is sql (STRUCTURE QUERY LANGUAGE)

It is a non procedural language which is used to communicate with any database such as Oracle, sqlserver etc.

This Language was developed by the German Scientist Mr. E.F.Codd in 1968.

ANSI (American National Standard Institute) approved this concept and in 1972 sql was released into the market.

Features of SQL:

SQL is not a case sensitive language it means that all the commands of Sql are not case sensitive.

Every command of sql should ends with a semicolon (;) (It is exemption for SQL Server)

SQL can be pronounced as Sequel (Structured English Query Language)

SQL can be called as Common Language Interface, which is used to communicate with any type of database.

SQL can be called as NLI (Natural Language Interface). It means that all the SQL Commands are almost similar to normal English language.

Structured query language is mainly divided into 4 sub languages

1. DDL (Data Definition Language)

2. DML (Data Manipulation Language)

3. TCL (Transaction Control Language)

4. DCL(Data Control Language)

about sql

what is SQL server

Sql server  is a collection of databases where a database is a again a collection of various objects  likes tables , views procedures , function, triggers, Indexes   etc.

Database under into sql server are divided into two  types

  1. System Database
  2. User Database
System Database

The databases are used by sql for the functionality of sql server and  without there data bases the server will not function users of sql server are not given a direct support for  updating the information under system data bases . the system data bases include  these  four databases.

  1. Master
  2. Model
  3. MsdB
  4. Tempdb
Master :-

These database records on the system level information under associated with the server.

Model:-

It is used as a template for all new databases created on sql server data base . i.e. whenever we create   a  new data base a copy of the  model data base is taken and given with a new name.

MSDB :-

It is used for recording or storing information about alerts, jobs etc that are   per formed  by sql server agent.

Tempdb :-

It is used for holding the temporary tables that are  created under  various databases . once we restart the  server the  tempdb  data base   is destroyed and again that  are created previairly.

 

User  data bases: 

These are databases created and managed by the users  for sorting their objects like tables views extra.