sql - 如何将 SQL 查询的 xml 输出转换为 varchar 输出

Question

我正在尝试生成

SELECT DISTINCT
        P.DOMAIN_ID,
        P.SOURCE_SYSTEM_ID
FROM    EDW.dbo.DOMAIN_VALUE AS P
WHERE   P.ID = 4
        AND CURRENT_FLAG = 'Y'
EXCEPT
( SELECT    F.DOMAIN_ID,
            F.SOURCE_SYSTEM_ID
  FROM      EDW.dbo.DOMAIN AS F
  WHERE     F.ID = 4
            AND F.CURRENT_FLAG = 'Y'
)
FOR     XML PATH('DOMAIN'),
            ROOT('DOMAIN_VALUE')  

结果选项卡中的 XML 输出值为

<REFERENCE_DOMAIN_VALUE>
   <REFERENCE_DOMAIN>
       <REFERENCE_DOMAIN_ID>10799</REFERENCE_DOMAIN_ID>
       <REFERENCE_SOURCE_SYSTEM_ID>7452-001</REFERENCE_SOURCE_SYSTEM_ID>
   </REFERENCE_DOMAIN>
</REFERENCE_DOMAIN_VALUE>

现在我需要将此 XML 转换为 varchar(max)，但结果需要相同。

Answer 1

只需将其子查询为标量值并进行转换。这里的技巧是 FOR XML in a subquery 和 EXCEPT on top 不要混在一起，所以先子查询 EXCEPT 部分。

SELECT CONVERT(varchar(max), (
    SELECT * FROM (
        SELECT DISTINCT P.DOMAIN_ID, P.SOURCE_SYSTEM_ID
        FROM EDW.dbo.DOMAIN_VALUE AS P
        WHERE P.ID = 4 AND CURRENT_FLAG = 'Y'
        EXCEPT (
        SELECT F.DOMAIN_ID, F.SOURCE_SYSTEM_ID
        FROM EDW.dbo.DOMAIN AS F
        WHERE F.ID = 4 AND F.CURRENT_FLAG = 'Y' )
    ) I
    FOR XML PATH('DOMAIN'), ROOT('DOMAIN_VALUE')
))