假設現在有如下N條記錄 表明叫book
id author title
1 aaa AAA
2 bbb BBB
3 ccc CCC
4 ddd DDD
5 eee AAA
現在想從這5條記錄中查詢所有title不重復的記錄
select distinct title,author from book這樣是不可以的 因為distinct只能作用于一個字段
想請教應該怎么寫

答案:
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

如果選第一條符合的記錄，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