DROP命令属于（)操作

A.CREATE

B.GRANT

C.UPDATE

D.DROP

A.CREATE，DROP，GRANT

B.CREATE，DROP，ALTER

C.CREATE，DROP，UPDATE

D.CREATE，DROP，SELECT

A.update

B.alter

C.create

D.drop

A.数据操作语言(OML)

B.数据定义语言(DDL)

C.数据查询语言(DQL)

A.CREATE FILE

B.DROP RULE

C.DROP PROC

D.DELETE PROC

A.DROP

B.UPDATE

C.SELECT

D.USE

A．alter table tb_book drop isbn char

D．update table tb_book drop isbn

A.DELETE

B.DROP

C.CLEAR

D.REMOV