关联子查询 Update 语句更新数据 无 --方法1：Update?Table1?set?c?=?(select?c?from?Table2?where?a?=?Table1.a)?where?c?is?null?--方法2：update??Aset??newqiantity=B.qiantityfrom??A,Bwhere??A.bnum=B.bnum?--方法3：update????(select?A.bnum?,A.newq
关联子查询Update语句更新数据
--方法1： Update?Table1?set?c?=?(select?c?from?Table2?where?a?=?Table1.a)?where?c?is?null? --方法2： update??A set??newqiantity=B.qiantity from??A,B where??A.bnum=B.bnum? --方法3： update ????(select?A.bnum?,A.newqiantity,B.qiantity?from?A?left?join?B?on?A.bnum=B.bnum)?AS?C set?C.newqiantity?=?C.qiantity where?C.bnum?=XX?
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