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DDL,DML,DCL区别

原创 Linux操作系统 作者:pennycheung 时间:2009-01-09 16:13:49 0 删除 编辑
DDL is Data Definition Language statements. 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
  • GRANT - gives user's access privileges to database
  • REVOKE - withdraw access privileges given with the GRANT command

DML is Data Manipulation Language statements. 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
  • CALL - call a PL/SQL or Java subprogram
  • EXPLAIN PLAN - explain access path to data
  • LOCK TABLE - control concurrency

DCL is Data Control Language statements. Some examples:

  • 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 what rollback segment to use
 

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