在redshift中使用DISTINCT的listagg

Question

我在努力寻找一个好办法,做一个DISTINCT在listagg中红移.

我想要做的就是列出产品组合,但每行应该返回一个不同产品的列表.

例

期望的输出:

bulb, light
bulb, light, fan

代替:

bulb, bulb, light
bulb, bulb, light, fan

下面是我的SQL:

select
    tit.listagg  
from (
    SELECT
        username,
        listagg(node_name, ',')
        WITHIN GROUP (ORDER BY node_name asc)
    FROM table
    Where node_type not like '%bla bla%'
    GROUP BY username
) as tit
group by listagg;

Answer 1

您可以枚举行,然后选择第一行:

select username,
       listagg(case when seqnum = 1 then node_name end, ',') within group (order by node_name asc) 
from (select t.*,
             row_number() over (partition by username, node_name order by node_name) as seqnum
      from table t
      where node_type not like '%bla bla%' 
     ) t
group by username;

这使用listagg()忽略NULL值的功能.