【数据库】 关联多表删除重复数据

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delete table from table a, (     select b.val1 ,b.val2 ,COUNT(1) as cnt     from table b     group by b.val1 ,b.val2     haval1g COUNT(1) > 1 )b where a.val1 = b.val1 and a.val2 = b.val2 and a.id not in (     select MAX(id) as id     from table a     group by val1 ,val2     haval1g COUNT(1) > 1 )