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A Data Definition Language (DDL) is used to converse (more usually, to issue commands) regarding the structures in which data is or will be stored.

Example data definition statements in the SQL language, for relational DBMSes:

  • 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

See also: DML, DCL, TCL.