有这样一张表，表数据及结果如下：
| school_id | school_name | total_student | test_takers |
| 1239 | abraham lincoln high school | 55 | 50 |
| 1240 | abraham lincoln high school | 70 | 35 |
| 1241 | acalanes high school | 120 | 89 |
| 1242 | academy of the canyons | 30 | 30 |
| 1243 | agoura high school | 89 | 40 |
| 1244 | agoura high school | 100 | 50 |
我们可以看出，school_name的字段值有重复数据(abraham lincoln high school 和agoura high school分别出现两次)，那么如何删除这两条数据，从而只让这两个数值出现一次呢？ 具体实现方法如下：
1、删除重复记录,保存id最小的一条
delete from `test` where `school_name` in (select `school_name`
from `test`
group by `school_name`
having count( * ) >1) and school_id not in (select min(school_id) from test group by school_id having count(* )>1)
先使用group by having语法查询出重复的数据，然后删除重复数据并保留school_id最小的一条.
2、删除重复记录,保存id最大的一条
delete from `test` where `school_name` in (select `school_name`
from `test`
group by `school_name`
having count( * ) >1) and school_id not in (select max(school_id) from test group by school_id having count(* )>1)
原理和上面一样。
以上就是mysql查找删除重复数据并只保留一条实例详解，希望能帮助到大家，谢谢大家对本站的支持！
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