更新一个表的字段值等于另一个表的字段值的SQL语句

将id相同的B表的name更新到A表

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表a 字段id??? name????? 表b? id?? name

??????????? 1????? aa???????????????? 1??? aa

???????????? 2???? bb??????????????????2??? kk

??????????? 3????? cc???????????????????3?? mm

??????????? 4?????? ll

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UPDATE a t
SET name = (SELECT name FROM b WHERE ID = t.ID)
WHERE EXISTS (SELECT 1 FROM b WHERE ID = t.ID AND name != t.name)

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更新后A的结果

????????? 1????? aa?????????????????

??????????2??????kk????????????????

??????????3??????mm???????????????

????????? 4?????? ll

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