Question

我在SQL查询中使用了WM_CONCAT。数据库已更新至版本12c，WM_CONCAT不起作用。

查询具有价值：

Select r.product_id, count (1) how_many, wm_concat (distinct r.number) numbers From ...

如何将其转换为LISTAGG函数。我尝试了这个，但是没用：

Select r.product_id, count(1) how_many, LISTAGG(r.number, ',') WITHIN GROUP (order by r.number) numbers From ...

Answer 1

您应该在查询中添加分组依据

with tab as(
  select '10' as num, 'A' as product from dual union all
  select '10' as num, 'B' as product from dual union all
  select '10' as num, 'C' as product from dual union all
  select '10' as num, 'D' as product from dual union all
  select '20' as num, 'A' as product from dual union all
  select '20' as num, 'B' as product from dual union all
  select '30' as num, 'A' as product from dual
)

select  product
, count (1) how_many
, LISTAGG(num, ',') WITHIN GROUP (order by num) 
from tab
group by product

但您必须小心，因为使用listagg只能连接最大4K的字符串。还有其他字符串聚合技术，请看答案here。

PRODUCT | HOW_MANY | LISTAGG(NUM,',')WITHINGROUP(ORDERBYNUM)
:------ | -------: | :--------------------------------------
A       |        3 | 10,20,30                               
B       |        2 | 10,20                                  
C       |        1 | 10                                     
D       |        1 | 10

db <>提琴here

将WM_CONCAT函数更改为LISTAGG

1 个答案: