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SQL Programming

Last Updated: Jun 06, 2018
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SQL Commands

The standard SQL commands to interact with relational databases are CREATE, SELECT, INSERT, UPDATE, DELETE and DROP. These commands can be classified into the following groups based on their nature,

DDL - Data Definition Language

DDL is short name of Data Definition Language, which deals with database schemas and descriptions, of how the data should reside in the database.

  • CREATE - create a new table, view for a table or other object in the database
  • ALTER - modifies an existing database object, such as a table
  • DROP - deletes an entire table, a view of a table or other objects in 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

DML is short name of Data Manipulation Language which deals with data manipulation and includes most common SQL statements such SELECT, INSERT, UPDATE, DELETE etc, and it is used to store, modify, retrieve, delete and update data in a database.

  • SELECT - retrieves records from one or more tables
  • INSERT - creates a record
  • UPDATE - modifies records
  • DELETE - deletes records
  • MERGE - UPSERT operation (insert or update)
  • CALL - call a PL/SQL or Java subprogram
  • EXPLAIN PLAN - interpretation of the data access path
  • LOCK TABLE - concurrency control

 

DCL - Data Control Language

DCL is short name of Data Control Language which includes commands such as GRANT and mostly concerned with rights, permissions and other controls of the database system.

  • GRANT (Grant privilige(s) to user)
  • REVOKE (Remove granted privilige(s) from a user)

 

TCL - Transaction Control Language

TCL is short name of Transaction Control Language which deals with a transaction within a database.

 

  • COMMIT - commits a transaction
  • ROLLBACK - rollback a transaction in case of any error occurs
  • SAVEPOINT - to rollback the transaction making points within groups
  • SET TRANSACTION - specify characteristics of the transaction

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