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The author:(作者)delv
published in(发表于) 2013/12/30 4:38:45
SQL中的DDL，DML，DCL语言_mssql学习_编程技术

SQL中的DDL,DML,DCL语言_mssql学习_编程技术-你的首页-uuhomepage.com
感觉自己是比较笨的，学习过SQL语言，但是却分不太清楚DDL、DML、DCL语言，所以呢，今天就厚着脸皮问了老师，现在就自己目前的了解来总结一下。
1、DDL（DATA DEFINITION LANGUAGE）数据描述语言
DDL语句不会产生还原数据，所以删除的数据也是无法恢复的
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
2、DML（DATA MANIPULATION LANGUAGE）数据操纵鱼语言
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
3、DCL（DATA CONTROL LANGUAGE）数据控制语言
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
感觉是要好那么一点了，至少不那么糊涂了，毕竟自己也学了那么久，不能什么都不知道三，不能只晓得就一个create、update、drop，嘿嘿！！！


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