Question

我正在尝试使用UPDATE和INNER JOIN的东西查询而没有成功。我需要将查询结果填充到一个列/行中，并使用该结果更新另一个表。

我目前的代码就是这个。

Update t1
SET t1.col1 = t2.ordernotes 
FROM db.dbo.table1 t1
INNER JOIN 
    STUFF((
            (Select order_no, Notes As ordernotes
            FROM db.dbo.table2
            GROUP BY order_no
            ORDER BY TimeStamp
            FOR XML PATH('')
            ),1,1,'')
            As t2
ON t2.order_no = t1.order_no

内部联接中的查询返回以下结果

Order_no | OrderNotes
1234     | Note 1
1234     | Note 2
1234     | Note 3

所需的结果是这个，然后更新到表1

Order_no | OrderNotes
1234     | Note 1, Note 2, Note 3

Answer 1

一种方法使用cross apply：

Update t1
    SET t1.col1 = t2.ordernotes 
    FROM db.dbo.table1 t1 CROSS APPLY
         (SELECT STUFF((SELECT ', ' + t1.Notes
                        FROM db.dbo.table2
                        WHERE t2.order_no = t1.order_no
                        ORDER BY t2.TimeStamp
                        FOR XML PATH('')
                       ), 1, 2, ''
                      ) as ordernotes
         ) t2;

但是，最好养成使用type进行字符串连接的习惯：

Update t1
    SET t1.col1 = t2.ordernotes 
    FROM db.dbo.table1 t1 CROSS APPLY
         (SELECT STUFF((SELECT ', ' + t1.Notes
                        FROM db.dbo.table2
                        WHERE t2.order_no = t1.order_no
                        ORDER BY t2.TimeStamp
                        FOR XML PATH(''), TYPE
                       ).VALUE('.', 'nvarchar(max)'
                              ), 1, 2, ''
                      ) as ordernotes
         ) t2;

将UPDATE与INNER JOIN和STUFF函数结合使用

1 个答案: