Oracle只取第一行

1. 伪列rownum，不能用于排序和分组，除非套一层select

select col01,col02 from table1 where rownum = 1;

select col02, col02 from (select col01, col02 from table1 order by col02 ) where rownum = 1;

2. row_number() over()，必须套一层select

select * from (
  select col01,col02,
  row_number() over(partition by col03 order by col05 DESC) as num2
  from table1 t1
) t2
where t2.num2=1;

参考资料：E11882_01/server.112/e41084/functions156.htm#i86310

3. fetch first 版本12c才支持

select col01, col02
from table1 
order by col03
fetch first 1 rows only;

4. offset fetch next 版本12c才支持

select col02, col02
from table1
order by col03
offset 1 rows fetch next 1 rows only;