Question

我有一个包含许多（30+）列和~250k行的表。我想取三个列（GroupId，Name和Species），按GroupId对它们进行分组，并将多行的Species字段连接成一个。

例如，以下数据：

1     NameA     Cat
2     NameA     Dog
3     NameA     BigBird
4     NameB     Chicken
6     NameC     Wolf
7     NameC     Lion

期望的结果：

1     NameA     Cat,Dog,BigBird
2     NameB     Chicken
3     NameC     Wolf,Lion

此SQL将数据分组在一起：

SELECT GROUPID, NAME, SPECIES,
ROW_NUMBER() OVER (partition by GROUPID order by SPECIES) r
from TableName;

如何组合每个组的Species字段并使用以逗号分隔的列表创建字段？

Answer 1

自Oracle 11g起，您可以使用listagg()：

select NAME
     , listagg(SPECIES, ', ') within group (order by GROUPID) as "SPECIES"
from TableName
group by NAME

如果您只想要唯一值：

select NAME
     , listagg(SPECIES, ', ') within group (order by GROUPID) as "SPECIES"
from (
   select distinct NAME
        , SPECIES
   from TableName
) t
group by NAME

或wm_concat()：

select NAME
     , wm_concat(distinct SPECIES) as "SPECIES"
from TableName
group by NAME

Answer 2

对于SQL更喜欢这个查询：

select 
    row_number() over(order by name) as group_id, name,
    stuff( (select ',' + species  
            from tbl_species s1
            where tbl_species.name = s1.name
            for xml path('') ), 1, 1, '') as species
 from 
     tbl_species 
 group by 
     name

https://sqlwhisper.wordpress.com/2013/03/24/stuff-and-for-xml-path-for-string-concatenation/

您可以参考此网站，详细了解stuff和for xml path

如何将多行中的字段组合到分隔列表中？

2 个答案: