Oracle - DDL, DML and DCL commands

1)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

2)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 data
* LOCK TABLE - control concurrency

3)DCL - Data Control Language. Some examples:
* GRANT - gives user's access privileges to database
* REVOKE - withdraw access privileges given with the GRANT command

4)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 - 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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