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MORE ON DATABASE                                                    5











                   Data in a database can be stored and manipulated by using SQL. SQL is Structured Query Language
                   for storing, manipulating and retrieving data from a database. In this chapter, we will learn about
                   different type of commands.
                      TYPES OF DATABASE COMMANDS

                   S   uses various commands to perform different operations on a database. Such commands are
                   categorised into:
                      ata  efinition  anguage                           ata Manipulation  anguage   M
                      ata  ontrol  anguage                              ransaction  ontrol  anguage

                    ata  efinition  anguage

                      ata  efinition  anguage or  ata  escription  anguage       is a standard for commands
                   that define the different structures in a database.     statements create  modify and remove
                   database objects such as tables, indexes and users. Common DDL statements are CREATE, ALTER,
                   TRUNCATE, RENAME and DROP.
                    ata Mani ulation  anguage   M

                      ata Manipulation language   M   is a language that enables users to retrieve  update  insert and
                   delete data in a database. Common DML statements are SELECT, UPDATE, INSERT INTO and DELETE.
                     ata  ontrol  anguage

                   A Data Control Language is a language that has various commands which are used to grant and
                   take back authority from any database user. Some DCL statements are Grant and Revoke.

                   Transaction  ontrol  anguage  T
                   A Transaction Control Language is a language that has various commands which are used to
                   manage transactions in the database.  These are used to manage the changes made by DML
                   statements. Some TCL statements are Commit, Savepoint and Rollback.
                      Do you know?


                        popular data manipulation language is Structured  uery  anguage  S   .


                       DATABASES AND OPERATORS

                     data type defines a sort of value that a column should contain. In a database table  every column
                   must have a name and data type.


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