Types of DBMS languages

Data Definition Language (DDL) : Statements are used to define the database structure or schema.

Some examples:

  • CREATE - to create objects in the database
  • ALTER - alters the structure of the database
  • DROP - delete objects from the database
  • TRUNCATE - remove all records from a table, including all spaces allocated for the records are removed
  • COMMENT - add comments to the data dictionary
  • RENAME - rename an object

  • Data Manipulation Language (DML) : Statements are used for managing data within schema objects.

    Some examples:

  • SELECT - Retrieve data from the a database
  • INSERT - Insert data into a table
  • UPDATE - Updates existing data within a table
  • DELETE - deletes all records from a table, the space for the records remain
  • MERGE - UPSERT operation (insert or update)
  • CALL - Call a PL/SQL or Java subprogram
  • EXPLAIN PLAN - explain access path to data
  • LOCK TABLE - control concurrency

  • Data Control Language (DCL)
    Some examples:

  • GRANT - gives user's access privileges to database
  • REVOKE - withdraw access privileges given with the GRANT command

  • Transaction Control (TCL) : Statements are used to manage the changes made by DML statements. It allows statements to be grouped together into logical transactions.

    Some examples:

  • COMMIT - save work done
  • SAVEPOINT - identify a point in a transaction to which you can later roll back
  • ROLLBACK - restore database to original since the last COMMIT
  • SET TRANSACTION - Change transaction options like isolation level and what rollback segment to use

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