Question

以下是我的代码。

DECLARE @msg NVARCHAR(MAX) = NULL

;WITH CTE AS (
                    SELECT 'A' AS Message
                UNION
                    SELECT 'B' AS Message
                UNION
                    SELECT 'C' AS Message
                UNION
                    SELECT 'D' AS Message
)

SELECT @msg = COALESCE(ISNULL(@msg,'Attachements') + ', ','') +  Message FROM CTE

SELECT @msg + ' are missing.'

正在产生输出： -

Attachments, A, B, C, D are missing.

我怎样才能避免在＃34; Attachments＆＃34;之后的第一个逗号。？请帮忙。

也欢迎满足要求的其他技术。

感谢。

Answer 1

而不是使用undocumented/unsupported way of concatenating strings，而是使用FOR XML PATH：

DECLARE @msg NVARCHAR(MAX) = NULL

;WITH CTE AS (
    SELECT 'A' AS Message
    UNION
    SELECT 'B' AS Message
    UNION
    SELECT 'C' AS Message
    UNION
    SELECT 'D' AS Message
)

SELECT @msg = 'Attachments ' + 
    STUFF((
        SELECT ', ' + Message 
        FROM CTE
        ORDER BY Message
        FOR XML PATH(''), TYPE).value('.[1]', 'NVARCHAR(MAX)')
    , 1, 2, ' ')

SELECT @msg + ' are missing.'

Answer 2

试试这个：

SELECT @msg = ISNULL(@msg + ', ', 'Attachements ') +  Message FROM CTE

并查看FOR XML方法来连接字符串

Answer 3

用例

SELECT @msg = case when @msg is NULL then 'Attachment ' 
else
COALESCE(@msg + ', ','') 
end
+ Message FROM CTE
SELECT @msg + ' are missing.'

Answer 4

只需更改最后两行

SELECT @msg = COALESCE(@Msg + ', ','') +  Message FROM CTE

SELECT 'Attachments '+@msg + ' are missing.'

使用COALESCE函数在消息中附加消息

4 个答案: