假设现在有如下N条记录 表叫book
id author title
1 aaa AAA
2 bbb BBB
3 ccc CCC
4 ddd DDD
5 eee AAA
现在想从这5条记录中查询所有title不重复的记录
select a.* from book a right join ( select max(id) id from book group by title) b on b.id = a.id where a.id is not null
如果选第一条符合的记录，那么用min(id)就行了
select a.* from book a right join ( select min(id) id from book group by title) b on b.id = a.id where a.id is not null