在連接查詢在SQL服務器使用鑄造列名

Question

說我有一個這樣的查詢蒙上XML查詢

SELECT TOP 5 
    CAST (row.query('col(/xml/tag)'), as NVARCHAR(100)) AS 'foobar' 
FROM db.table 

如何使用在LEFT JOIN XML查詢的鑄造結果？

SELECT TOP 5 
    CAST (row.query('col(/xml/tag)'), as NVARCHAR(100)) AS 'foobar' 
FROM db.table 
LEFT JOIN db.table_table 
-- don't know the syntax for this part 
ON db.table['foobar'] = db.table_table.col 

Answer 1

爲原始查詢爲sub-select

SELECT foobar 
FROM (SELECT TOP 5 Cast (row.query('col(/xml/tag)') AS NVARCHAR(100)) AS foobar 
     FROM db.TABLE) t 
     LEFT JOIN db.table_table 
       ON t.foobar = db.table_table.col