01-01-2013, 02:09 PM
STUDY OF SQL COMMANDS
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PROBLEM STATEMENT:
To study about SQL commands, DDL(Data Definition Language), DML(Data Manipulation Language) and DCL(Data Control Language).
SQL – STRUCTURED QUERY LANGUAGE:
The SQL consists of facilities for defining, accessing and managing rational database. Getting inspiration from the success of system R, software companies other than IBM also began developing process that implemented SQL and the first product that comes out was ORACLE from the relational software inc. SQL is a high level language. It is extremely flexible and provides a greater degree of abstraction than procedural languages. It is divided into the following categories.
DDL (Data Definition Language)
DML (Data Manipulation Language)
DCL (Data Control Language)
PROBLEM DESCRIPTION:
Data definition language is used to define the database schema. The DDL commands are CREATE, ALTER, DROP, TRUNCATE, RENAME. The DML is used to manipulate the data within the schema. DML commands are SELECT, INSERT, UPDATE, DELETE. DCL is used to provide security for the database. DCL commands are COMMIT and ROLLBACK.