Question

这是我到目前为止所做的：

SELECT 
    account, ' ', message_type, 
    MAX(message_no) as max_message_no, message_text
FROM
    (SELECT 
         account, message_type, message_no, message_text
     FROM  
         messages m 
     INNER JOIN 
         receivables r ON m.account = r.aracct
     WHERE 
         m.account IN (SELECT r.aracct AS account 
                       FROM receivables r 
                       WHERE r.balance <> 0)
         AND m.message_type = 'N') t1
GROUP BY 
    t1.account, t1.message_type, t1.message_text

我不断收到错误消息：

text，ntext和image数据类型无法进行比较或排序，除非使用IS NULL或LIKE运算符。

我基本上想要每个帐户中的最大message_no，并且我希望它显示message_text，但它不会允许它，因为它是text数据类型。

Answer 1

TEXT，NTEXT和IMAGE已弃用，应替换为相应的类型VARCHAR(MAX)，NVARCHAR(MAX)和VARBINARY(MAX)。您可以使用

投射TEXT - 列

CAST(t1.message_text AS VARCHAR(MAX))

在您的子选择中可能足以执行此操作：

SELECT account, ' ', message_type, MAX(message_no) as max_message_no, message_text
FROM
(
SELECT account, message_type, message_no, CAST(message_text AS VARCHAR(MAX)) AS message_text
    FROM messages m INNER JOIN receivables r ON m.account = r.aracct
        WHERE m.account IN (SELECT r.aracct AS account FROM receivables r WHERE r.balance <> 0)
        AND m.message_type = 'N'
) t1
GROUP BY t1.account, t1.message_type, t1.message_text

Answer 2

您无法比较文字，图片，数据类型。如果您想使用它们，请将它们更改为Varchar或Nvarchar ..

下面的一些例子

   create table #t
    (
    yy text
    )

    insert into #t
    select '1'


    --fails
    select * from #t 
    where yy='1'
    /****
    Msg 402, Level 16, State 1, Line 1
    The data types text and varchar are incompatible in the equal to operator.**/

    --fails
    select yy from #t
    group by yy

    /****
    Msg 306, Level 16, State 2, Line 1
    The text, ntext, and image data types cannot be compared or sorted, except when using IS NULL or LIKE operator.
    ***/


    ---Workaround 
    --Try changing the datatypes involved to Varchar or Nvarchar
    select * from #t 
    where cast(yy as varchar(5))=1


    select cast(yy as varchar(10)) from #t 
    group by cast(yy as varchar(10))

<强>参考文献：
The text, ntext, and image data > types cannot be compared or sorted, except when using IS NULL or LIKE > operator

Answer 3

所以您查询的问题是您将其在主部分中投射为

SELECT account, ' ', message_type, MAX(message_no) as max_message_no, message_text
FROM
(
SELECT account, message_type, message_no, CAST(message_text AS VARCHAR(MAX)) AS message_text
    FROM messages m INNER JOIN receivables r ON m.account = r.aracct
        WHERE m.account IN (SELECT r.aracct AS account FROM receivables r WHERE r.balance <> 0)
        AND m.message_type = 'N'
) t1
GROUP BY t1.account, t1.message_type, CAST(message_text AS VARCHAR)

如何修复＆＃34; text，ntext和image数据类型无法进行比较或排序，除非使用IS NULL或LIKE运算符。＆＃34;

3 个答案: