if not exists(select 1 from sysobjects where type='U' and name='staffinfo')有什么作用?

// IF EXISTS (SELECT name FROM m if not exists (SELECT * From TA_ARTIFICER Where ARTID = @Artid)是什么意思?为什么要用到if not exists呢?在什么时候要用到 if not exists（）?它的作用是什么? if not exists(select 1 from sysobjects where type='U' and name='staffinfo')有什么作用? if exists (select 1 from #tmp_dj_xsg212 WHERE shangplx LIKE '%冷%' SQL关于IN和EXISTS的区别?请问2者到底有什么区别啊?select MC001 from BOMMC WHERE MC001 NOT IN (SELECT MD001 FROM BOMMD)和select MC001 from BOMMC WHERE MC001 NOT EXISTS (SELECT MD001 FROM BOMMD)2个IN查出来是80,而EXISTS查出来是 User does not exists user does not exists! insert into REC_OVER(ORG_ID) select '1' from dual where not exists (select ORG_ID from REC_OVER )insert into REC_OVER(ORG_ID) select '1' from dual where not exists (select ORG_ID from REC_OVER ) 请问oracle里这样的语句,为什么在sql/plus可 Distance is not a problem if true love exists是什么意思急 SQL查询选修了全部课程的学生姓名查询选修了全部课程的学生姓名：student 是学生表 course 是选课表 sc 是课程表select snamefrom studentwhere not exists（select *from coursewhere not exists (select *from scwhere sn 数据库SQL语句中 查询选修了全部课程的学生的学号和姓名 查询选修了全部课程的学生姓名.SELECT SnameFROM StudentWHERE NOT EXISTS（SELECT *FROM CourseWHERE NOT EXISTS(SELECT *FROM SCWHERE Sno= Student.SnoAND Cno= Cours 数据库 相关子查询 SELECT SNFROM SWHERE (NOT EXISTS( SELECT *FROM CWHERE NOT EXISTS( SELECT*FROM SCWHERE SNO =S.SNOAND CNO= C.CNO)))S为学生表 C为课程表 SC为选课情况 都是缩写啦 这是查询选修所有课程的学生姓名 但 user does not exists翻译 user does not exists是什么意思 exists是什么意思啊exists(select * from WE_Contract_Detail_Electricity where ContractID=@ContractID) exists If you love two persons,select the second; Because you will not love someone else if you truly love the source video file not exists