MYSQL数据库删除重复数据行
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下列Sql可用in,建议用exists
SELECT * FROM coldknow a WHERE EXISTS ( SELECT title, img FROM coldknow GROUP BY title, img HAVING (COUNT(1) > 1 AND a.title = title AND a.img = img) ) AND NOT EXISTS ( SELECT MIN(id) FROM coldknow GROUP BY title, img HAVING COUNT(1) > 1 AND MIN(id) = id )
a作为父表与虚拟子表进行关联,前exists存在父表字段与虚拟表相同的特征,后exists排除最小id的行,即保留重复记录中最小id的行
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