连接两个表的字符串的聚合函数？

Posted 2023-03-23

【中文标题】连接两个表的字符串的聚合函数？

【英文标题】：Aggregate function to concatenate strings joining two tables?

【发布时间】：2014-02-11 16:07:32

【问题描述】：

我知道如何使用 for xml auto 连接聚合查询中的字段。但是我在扩展该查询以使用两个表时遇到了一些问题，以下示例不起作用

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

【参考方案1】：

您应该能够将问题更改为以下内容以获得最终结果：

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