====== What are the difference between DDL, DML and DCL commands? ======

==== DDL ====

Data Definition Language statements are used to define the database structure or schema:

    * 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

==== DML ====

Data Manipulation Language statements are used for managing data within schema objects:

    * 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

==== DCL ====

Data Control Language statements:

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

==== TCL ====

Transaction Control statements are used to manage the changes made by DML statements. It allows statements to be grouped together into logical transactions.

    * 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