Question

在oracle里，多条返回结果，如何只能返回一条

如题。比如，就是，类似 select a,count(a) from table_a group by a
这样的效果，有没有哪个函数可以做到？

Answer 1

select a,count(a) from table_a group by a limit 1

或者：
top N

Answer 2

select * from (select a,count(a) from table_a group by a)

where rownum=1