怎样查得表中前六个记录的平均值？

Question

select avg(fld) from 
(select fld from tbl where rownum < 7 ) a

Answer 1

select avg(colname) from tbname where rownum<7;

Answer 2

如果colname有null值的话就有问题，
最好是这样
select sum(colanme)/6 from tbname where rownum<7;

Answer 3

SQL> select * from aa;ID         BB
---------- ----------
1          
2          
3     SQL> select avg(id) over(order by rownum rows 2 PRECEDING) from aa;AVG(ID)OVER(ORDERBYROWNUMROWS2
------------------------------
                             1
                           1.5
                             2select avg(sal) over(order by rownum rows 5 preceding) from tabname;