特此一记，省得忘。
1.DDL （Data Definition Language ）数据库定义语言 statements are used to define the database structure or schema.
DDL不需要commit.
CREATE
ALTER
DROP
TRUNCATE
COMMENT
RENAME
2.DML （Data Manipulation Language）数据操纵语言 statements are used for managing data within schema objects.
需要commit.
SELECT
INSERT
UPDATE
DELETE
MERGE
CALL
EXPLAIN PLAN
LOCK TABLE
3.DCL（Data Control Language）数据库控制语言 授权，角色控制等
GRANT 授权
REVOKE 取消授权
4.TCL（Transaction Control Language）事务控制语言
SAVEPOINT 设置保存点
ROLLBACK 回滚
SET TRANSACTION