SQL

DDL - Data Definition Language: statements 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

DML - Data Manipulation Language: statements 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 the data
    LOCK TABLE - controls concurrency

DCL - Data Control Language. Some examples:

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

TCL - Transaction Control: statements 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 - undo the modification I made since the last COMMIT
    SET TRANSACTION - Change transaction options like isolation level and what rollback segment to use
    SET ROLE - set the current active roles

DML are not auto-commit. i.e. you can roll-back the operations, but DDL are auto-commit.