聚合函数来连接连接两个表的字符串？

Question

我知道如何使用xml auto连接聚合查询中的字段。但是我有一些问题需要扩展该查询以便与两个表一起使用，下面的示例不起作用

例如，

set nocount on; 
declare @FirstTable table (RowID int, LinkedField int) 
insert into @FirstTable VALUES (1,1) 
insert into @FirstTable VALUES (2,2) 
insert into @FirstTable VALUES (2,3) 
insert into @FirstTable VALUES (2,4) 
insert into @FirstTable VALUES (3,5) 
insert into @FirstTable VALUES (3,1) 

declare @SecondTable table (LinkedField int, Field2Show int) 
insert into @SecondTable VALUES (1,11) 
insert into @SecondTable VALUES (2,12) 
insert into @SecondTable VALUES (3,13) 
insert into @SecondTable VALUES (4,14) 
insert into @SecondTable VALUES (5,15) 

/* 
output i need: 

RowID  ChildValues 
----------- ------------------- 
1   11 
2   12,13,14 
3   11,15 
*/ 

SELECT t1.RowID, 
STUFF(
      (SELECT ', ' + t2.Field2Show 
      FROM 
       (SELECT @SecondTable.Field2Show, @SecondTable.LinkedField 
       FROM @SecondTable 
       INNER JOIN @FirstTable ON   @FirstTable.LinkedField=@SecondTable.LinkedField) t2 
      WHERE t1.LinkedField = t2.LinkedField 
      ORDER BY t2.Field2Show 
      FOR XML PATH(''), TYPE).value('.','varchar(max)') ,1,2, '') AS ChildValues 
FROM @FirstTable t1 
GROUP BY t1.RowID 

Answer 1

你应该能够改变的问题如下，以得到最终结果：

SELECT distinct t1.RowID, 
STUFF(
      (SELECT ', ' + cast(t2.Field2Show as varchar(10)) 
      FROM @SecondTable t2 
      INNER JOIN @FirstTable t -- join on @FirstTable based on LinkedField 
       on t.LinkedField = t2.LinkedField 
      WHERE t1.RowID = t.RowID -- associate the RowId from FirstTable to concatenate 
      ORDER BY t2.Field2Show 
      FOR XML PATH(''), TYPE).value('.','varchar(max)') ,1,2, '') AS ChildValues 
FROM @FirstTable t1; 

见SQL Fiddle with Demo