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 * 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? User does not exists user does not exists! Distance is not a problem if true love exists是什么意思急 user does not exists翻译 user does not exists是什么意思 if not exists(select 1 from sysobjects where type='U' and name='staffinfo')有什么作用? exists If you love two persons selec,求翻译.这句话的意思是什么? // IF EXISTS (SELECT name FROM m the source video file not exists user does not exists这是什么意思? UnZIP fail.zip file not exists. if exists (select 1 from #tmp_dj_xsg212 WHERE shangplx LIKE '%冷%' if exists 括号后的条件如何写 python：os.path.exists(path) 和 os.path.lexists(path) 的区别os.path.exists(path)Return True if path refers to an existing path.Returns False for broken symbolic links.On some platforms,this function may return False if permission is not granted 在数据库中IF 和 IF EXISTS 有什么区别IF (条件)BEGIN语句快END和下面有什么区别?IF EXISTS (条件)BEGIN语句快END 英语翻译Radiographic examination will demonstrate the position of the alveolar margin and the condition of the alveolar bone.In a child or adolescent,radiographic examination may not be essential but if any doubt exists about the integrity of the