根据相同ID，对字符串列进行聚合【mysql,mssql】

TableA 

ID  Names

1   n1

2   n2

1  nn2

2  nn3

3  nn4

1  nn1

ID相同的记录，对Names进行聚合

得到结果是：

ID  SumNames

1   n1,nn2,nn1

2   n2,nn3

3   nn4

mysql 

select id,group_concat(names) from tableA group by id;

mssql

select stuff((select ','+names from tableA as t2 where t2.id=t1.id for xml path('')),1,1) from (select id,names from tableA as t1 group by id);

select stuff(  

(select ','+convert(Varchar(50),MemberGuid) from (SELECT a.MemberGuid,a.managerguid,b.UserName FROM membermanager a LEFT JOIN k_manager b ON a.managerguid = b.managerguid) as t2 where t2.
MemberGuid = t1.MemberGuid FOR XML PATH('')), 1, 1, ''   
) from (SELECT a.MemberGuid,a.managerguid,b.UserName FROM membermanager a LEFT JOIN k_manager b ON a.managerguid = b.managerguid) as t1
where memberguid=@MemberGuid group by memberguid