18-05-2012, 11:54 AM
Structured Query Language
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SQL
SQL is structured Query Language which is a computer
language for storing, manipulating and retrieving data
stored in relational database.
SQL is the standard language for Relation Database
System.
All relational database management systems like MySQL,
MS Access, Oracle, Sybase, Informix, postgres and SQL
Server uses SQL as standard database language.
Why SQL
Allow users to access data in relational database
management systems.
Allow users to describe the data.
Allow users to define the data in database and manipulate
that data.
Allow to embed within other languages using SQL
modules, libraries & pre-compilers.
Allow users to create and drop databases and tables.
Allow users to create view, stored procedure, functions in a
database.
Data Integrity
The following categories of the data integrity exist with each
RDBMS:
Entity Integrity : There are no duplicate rows in a table.
Domain Integrity : Enforces valid entries for a given column
by restricting the type, the format, or the range of values.
Referential integrity : Rows cannot be deleted, which are
used by other records.