Define DDL , DML , TCL

Data Definition Language ( DDL ) :
Data Definition Language are used to define the structure of a database or schema.
Some of the example includes statements like CREATE , ALTER , DROP etc.
Oracle Database implicitly commits the current transaction before and after every DDL statement.

Examples :

• CREATE - can be used to create a database , table , stored procedure.
• ALTER - can be used to alter the structure of databse table like add a new column.
• DROP - can be used to drop objects from database like drop a table.
• TRUNCATE - remove all records from a table . also remove all spaces allocated for the recods.
• COMMENT - can be used to add comments to data dictionary.
• RENAME - renames an object

Data Manipulation Language ( DML ) :

Data Manipulation Language can be used to modify / alter the data of existing schema objects. 

DML statements do not implicitly commit the current transactions.

Example :

• SELECT - used to retrive data from a database table.
• INSERT - used to insert new record in a table.
• UPDATE - can be used to update column values of a table.
• DELETE - can be used to delete records from a table.
• MERGE - insert or update operation.
• EXPLAIN PLAN - explain access path to data.
• CALL - can be used to call PL/SQL.
• LOCK TABLE - controls the concurrency.

Transaction Control Statements ( TCL ) :

Transaction Control Statements are used to control the manipulations made by Data Manipulation Language ( DML ) statements . 

Example :

• COMMIT - used to commit the transaction so that any changes made by the query are reflected by the database table.
• ROLLBACK - revert the changes that were made in the last commit.
• SAVEPOINT -  creates / identifies a point in the transaction to which you can rollback later.
• SET TRANSACTION - change transaction options like isolation level.

Session Control Statements  :

Session control statements dynamically manage the properties of a user session. These statements do not implicitly commit the current transaction.

Example :

• ALTER SESSION
• SET ROLE