样查得表中前六个记录的平均值?
如题。用SQL语句能实现吗?
select avg(fld) from
(select fld from tbl where rownum < 7 ) a
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select avg(colname) from tbname where rownum<7;
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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
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1
1.5
2
select avg(sal) over(order by rownum rows 5 preceding) from tabname;
游标中累加,读到6个求一次和。
游标结束在求一次和