DELETE FROM stu WHERE sno='57507111'; --通过修改表结构,来创建约束 ALTER TABLE stu ADD CONSTRAINT sno_pk PRIMARY KEY(sno); --删除约束 ALTER TABLE stu DROP CONSTRAINT sno_pk; --插入信息 INSERT INTO stu(sno,sbirthday) VALUES('57507105',TO_DATE('2017-04-02','YYYY-MM-DD')) --修改stu...