SELECT STUFF和where子句来缩小结果

Question

我有以下声明：

SELECT Stuff(
    (SELECT N', ' + activity FROM contact_categories FOR XML PATH(''),TYPE) 
    .value('text()[1]','nvarchar(max)'),1,2,N'') 

这显示从活动列的所有信息保存在一个字符串。我想要做的是将它作为一个字符串返回，但对于每个主键。

所以在表中它看起来像这样

Contact Activity 
1  Green 
1  Red 
1  Blue 
2  Green 
2  Red 
2  Blue 
3  Green 
3  Red 
3  Blue 

而不是显示它作为绿，青，绿，红，红，红，蓝，青，蓝都在一个字符串。我想它显示：

1 Green, Red, Blue 

2 Green, Red, Blue 

3 Green, Red, Blue 

我试图添加和where子句：

SELECT Stuff(
    (SELECT N', ' + activity FROM contact_categories FOR XML PATH(''),TYPE) 
    .value('text()[1]','nvarchar(max)'),1,2,N'') 
FROM contact_categories 
WHERE contact_number = # 

Answer 1

你应该使用GROUP BY

SELECT 
    contact, 
    Stuff(
    (SELECT N', ' + activity FROM contact_categories WHERE Contact = S.Contact FOR XML PATH(''),TYPE) 
    .value('text()[1]','nvarchar(max)'),1,2,N'') 
FROM contact_categories AS S 
GROUP BY contact 

Answer 2

SELECT distinct contact, Stuff(
    (SELECT N', ' + activity FROM contact_categories t2 WHERE t1.contact = t2.contact FOR 
    XML PATH(''),TYPE).value('text()[1]','nvarchar(max)'),1,2,N'') 
FROM contact_categories t1 

Answer 3

你有没有使用LISTAGG考虑？

---

SELECT contact, 
    listagg(activity, ', ') WITHIN GROUP (
ORDER BY 1) AS activity 
FROM contact_categories 
GROUP BY contact; 

https://docs.oracle.com/cd/E11882_01/server.112/e41084/functions089.htm#SQLRF30030