爲FOR XML EXPLICIT UNION結果分配給一個變量

Question

此查詢工作正常

SELECT 1 AS TAG, NULL AS parent, 1 [dog!1] 
UNION (SELECT 1,NULL, 3) 
FOR XML EXPLICIT, ROOT('dogs') 

我想將它分配給一個變量。這不工會工作正常：

DECLARE @x xml 
SET @x = ((
    (SELECT 1 AS TAG, NULL AS parent, 1 [dog!1] 
    FOR XML EXPLICIT, ROOT('dogs')) 
)) 

只要我介紹了工會這是行不通的：

DECLARE @x xml 
SET @x = ((
    (SELECT 1 AS TAG, NULL AS parent, 1 [dog!1] 
    UNION (SELECT 1,NULL, 3) 
    FOR XML EXPLICIT, ROOT('dogs')) 
    )) 

嘗試過各種各樣的事情。我缺少

Answer 1

你只需要添加更多的子查詢級是這樣的：

DECLARE @X XML = 
(
    SELECT * FROM 
    (
    SELECT 1 AS TAG, NULL AS parent, 1 [dog!1] 
    UNION 
    SELECT 1,NULL, 3 
)X 
    FOR XML EXPLICIT, ROOT('dogs') 
); 

SELECT @X;