Sql 如何高效地连接多个表中的多行

我有多个主表的外键表。表格如下所示：

姐妹

兄弟

叔叔

我需要将所有

IDNo

s串联在一起，但我似乎无法获得所有，例如，可能无法获得672

SELECT 
    ',' + S1.IDNo + ',' + B1.IDNo + ',' + U1.IDNo AS [text()] 
FROM 
    Sisters S1, Brothers B1, Uncles U1, MainTable 
WHERE 
    D1.MainID = MainTable.ID 
    AND S1.MainID = MainTable.ID 
    AND B1.MainID = MainTable.ID 
FOR XML PATH('')

后来我试着把桌子分开，然后再做凹面，但这样做的速度要慢得多。我能做什么

预期产出：

---

根据预期的输出，3个表中的每个表中的MainID列似乎在输出中没有发言权（如果有），那么这应该对您有用，尽管我不确定它是否可以扩展到处理600K+记录。出于好奇，为什么要连接这么大的值列表

Declare @x as varchar(max) = ''

SELECT @x = @x + ',' + CAST(A.IDNO as varchar)  FROM
(
select 1 as IDNO UNION ALL
select 2 as IDNO UNION ALL
select 3 as IDNO UNION ALL
select 4 as IDNO 
) A -- Pretend this is your Sisters tables
FOR XML PATH('')
PRINT @X -- Just for Debugging Purposes

SELECT @x = @x + ',' + CAST(B.ID as varchar)  FROM
(
select 55 as IDNO UNION ALL
select 66 as IDNO UNION ALL
select 77 as IDNO UNION ALL
select 88 as IDNO 
) B -- Pretend this is your Brothers tables

PRINT @X -- Just for Debugging Purposes

SELECT @x = @x + ',' + CAST(C.IDNO as varchar)  FROM
(
select 555 as IDNO UNION ALL
select 666 as IDNO UNION ALL
select 777 as IDNO UNION ALL
select 888 as IDNO 
) C -- Pretend this is your Uncles tables


PRINT @X -- Final Output 
SELECT @X as XML_Output FOR XML PATH('') 

输出：

,1,2,3,4
,1,2,3,4,55,66,77,88 
,1,2,3,4,55,66,77,88,555,666,777,888 -- Final Result

<XML>,1,2,3,4,55,66,77,88,555,666,777,888</XML> -- XML Output

---

仅供参考：主表约有200000条记录，子表各约有60000条记录。-在ANSI-92 SQL标准（20多年前）中，旧式的逗号分隔的表列表样式被正确的ANSI

JOIN

语法所取代，并且它的使用非常简单discouraged@marc_s我也使用了连接。速度没有太大影响。可恢复，您希望

联合所有人

，但没有示例结果，这仅仅是猜测。这并不是关于速度，而是关于可读性和可维护性，以及避免意外的交叉连接（笛卡尔产品）……好吧，我想要这个列表，因为客户希望从子表中搜索带有idno的主项。虽然我不知道还有没有别的办法，但我想到的最合理的办法就是这个。例子；如果客户端搜索

555

在IDs中，我应该显示ID号为111111的主项，考虑到我问题中的情况。

SELECT 
    ',' + S1.IDNo + ',' + B1.IDNo + ',' + U1.IDNo AS [text()] 
FROM 
    Sisters S1, Brothers B1, Uncles U1, MainTable 
WHERE 
    D1.MainID = MainTable.ID 
    AND S1.MainID = MainTable.ID 
    AND B1.MainID = MainTable.ID 
FOR XML PATH('')

,1,1,1,1,2,555,333,111,222,321,561,121,331,451,672

Declare @x as varchar(max) = ''

SELECT @x = @x + ',' + CAST(A.IDNO as varchar)  FROM
(
select 1 as IDNO UNION ALL
select 2 as IDNO UNION ALL
select 3 as IDNO UNION ALL
select 4 as IDNO 
) A -- Pretend this is your Sisters tables
FOR XML PATH('')
PRINT @X -- Just for Debugging Purposes

SELECT @x = @x + ',' + CAST(B.ID as varchar)  FROM
(
select 55 as IDNO UNION ALL
select 66 as IDNO UNION ALL
select 77 as IDNO UNION ALL
select 88 as IDNO 
) B -- Pretend this is your Brothers tables

PRINT @X -- Just for Debugging Purposes

SELECT @x = @x + ',' + CAST(C.IDNO as varchar)  FROM
(
select 555 as IDNO UNION ALL
select 666 as IDNO UNION ALL
select 777 as IDNO UNION ALL
select 888 as IDNO 
) C -- Pretend this is your Uncles tables


PRINT @X -- Final Output 
SELECT @X as XML_Output FOR XML PATH('') 

,1,2,3,4
,1,2,3,4,55,66,77,88 
,1,2,3,4,55,66,77,88,555,666,777,888 -- Final Result

<XML>,1,2,3,4,55,66,77,88,555,666,777,888</XML> -- XML Output

Declare @x as varchar(max) = ''
SELECT  @x = @x + ',' + CAST(A.IDNO as varchar)  FROM
(
select MainID ,   IDNO FROM SISTERS  UNION ALL
select MainID ,   IDNO FROM BROTHERS UNION ALL
select MainID ,   IDNO FROM UNCLES
) A


SELECT @X as XML_Output FOR XML PATH('')