标题: 关于update的疑惑 [打印本页] 作者: lang_zhong 时间: 2005-12-16 12:58 标题: 关于update的疑惑 表CPRIZE 的主键是badge
请看下面2个语句
UPDATE CPRIZE c SET c.DIRECSTD=
(SELECT SUM(a.DIRECSTD) FROM CPRIZETWO a WHERE a.badge=c.badge)
WHERE EXISTS (SELECT 1 FROM CPRIZETWO a WHERE a.badge=c.badge);
与
UPDATE CPRIZE c SET c.DIRECSTD=
(SELECT SUM(a.DIRECSTD) FROM CPRIZETWO a WHERE a.badge=c.badge)
WHERE EXISTS (SELECT SUM(a.DIRECSTD) FROM CPRIZETWO a WHERE a.badge=c.badge);
原以为是一样的,运行的结果出乎意料
第二个语句居然跟下面语句一个效果,昏倒!
UPDATE CPRIZE c SET c.DIRECSTD=
(SELECT SUM(a.DIRECSTD) FROM CPRIZETWO a WHERE a.badge=c.badge);