mysql查找删除重复数据,只保留一条

我们可以看出,name字段有重复数据,(华师一附中出现了两次),如何删除重复数据保留其中的一条呢?具体实现方案如下:

1.删除重复字段,保留id最小的一条

delete FROM `t_school_name` WHERE 
`name` in 
(select name from (SELECT `name` FROM `t_school_name` GROUP BY `name` HAVING COUNT( * ) >1) ) 
and id not in 
(select id from (select min(id)  from t_school_name group by name having count(* )>1) )

  先使用 group by having count(1)>1找出重复字段,然后删除数据,保留id最小的数据.

2.删除重复字段,保留id最大的以调

delete FROM `t_school_name` WHERE 
`name` in 
(select name from (SELECT `name` FROM `t_school_name` GROUP BY `name` HAVING COUNT( * ) >1) ) 
and id not in 
(select id from (select max(id)  from t_school_name group by name having count(* )>1) )

先使用 group by having count(1)>1找出重复字段,然后删除数据,保留id最大的数据.