删除ReaderType表中所有数据，正确的命令是 A: DELETE TABLE ReaderType B: DELETE ReaderType C: DROP TABLE ReaderType D: DROP ReaderType

删除ReaderType表中“企业职工”的信息，正确的语句是

以下语句表示_____连接。（填汉字）SELECT Reader.*,ReaderType.* FROM Reader INNER JOIN ReaderType ON Reader.TypeID=ReaderType.TypeID

以下语句从__个表中进行查询。（填数字）SELECT Reader. *,ReaderType.* FROM Reader, ReaderType where Reader.TypeID=ReaderType.TypeID

智慧职教: 更新borrow表每条借书记录的eprdate(到期日期)。 borrow  eprdate=timestampadd(day,(select maxdays from readertype where typeID in (select typeID from reader where reader.readerID=.)),brwdate);

为表ReaderType的LimitNum字段添加检查约束，要求教该字段的值<3，正确的语句是 A: ALTER TABLE ReaderTypeADD CONSTRAINT CK_ReaderType_LimitNum check (LimitNum=3) B: ALTER TABLE ReaderTypeADD CONSTRAINT check (LimitNum<3) C: ALTER TABLE ReaderTypeADD CONSTRAINT CK_ReaderType_LimitNum (LimitNum<3) D: ALTER TABLE ReaderTypeADD CONSTRAINT CK_ReaderType_LimitNum check (LimitNum<3)

为表ReaderType的LimitNum字段添加检查约束，要求教师类型中该字段的值+3，正确的语句是 A: ALTER TABLE ReaderTypeADD CONSTRAINT CK_ReaderType_LimitNum check (LimitNum=LimitNum+3) B: ALTER TABLE ReaderTypeADD CONSTRAINT check (LimitNum=LimitNum+3) WHERE Typename='教师' C: ALTER TABLE ReaderTypeADD CONSTRAINT CK_ReaderType_LimitNum (LimitNum=LimitNum+3) WHERE Typename='教师' D: ALTER TABLE ReaderTypeADD CONSTRAINT CK_ReaderType_LimitNum check (LimitNum=LimitNum+3) WHERE Typename='教师'