Question

我需要在有序行上为某些空值分配一个等级我的查询是这样的：

with sub as 
(
 select 10 as id, 1 as inx,2 as num from dual
  union all
 select 10 as id, 2 as inx,null as num from dual
  union all
 select 10 as id, 3 as inx,8 as num from dual
  union all
 select 10 as id, 4 as inx,null as num from dual
)
select *
  from sub order by inx

，结果集如下：

id  inx  num
---------- 
10  1    2
10  2    null
10  3    8
10  4    null

我想用先前的第一个非空值设置空值例如：num null值应为“2”，其中inx = 2
和num null值应为“8”，其中inx = 4，依此类推。

thx任何想法..

Answer 1

如果您知道值正在增加，则可以使用max()：

select id, inx, max(num) over (partition by id order by inx) as num

如果它们没有增加且多个空值永远不会出现在序列中，则可以使用lag()：

select id, inx,
       (case when num is null
             then lag(num) over (partition by id order by inx)
             else num
        end)as null;

如果序列中出现空值，则可以使用ignore nulls选项lag()：

select id, inx,
       (case when num is null
             then lag(num ignore nulls) over (partition by id order by inx)
             else num
        end)as null

如何在oracle中使用先前的第一个非null值为空值赋值

1 个答案: