sql - oracle listagg 结果太长

Question

我listagg()用来聚合字符串值

例如，有一个这样的表：

Table1
Name     Rank
Bob      A
Bob      B
Bob      C
Tom      A
Tom      C

SELECT Name,LISTAGG(RANK,';') WITHIN GROUP (ORDER BY RANK) AS COMRANK 
FROM Table1

我们得到结果：

Name  COMRANK
Bob   ABC
Tom   AC

如果 COMRANK 变得太长怎么办？我可以在汇总之前找到 top xxx 吗？

Answer 1

您可以使用窗口函数对行进行排名，并将行限制为您需要的任何排名。

SELECT Name,LISTAGG(RANK,';') WITHIN GROUP (ORDER BY RANK) AS COMRANK 
FROM (select
    name, rank,
    rank() over (partition by name order by rank) rnk
  from Table1
) where rnk < 10; --some value
GROUP BY Name;