如何解決「除非使用IS NULL或LIKE運算符，否則不能比較或排序文本，ntext和圖像數據類型。」

Question

這是我到目前爲止有：

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 

我不斷收到錯誤消息：

文本，ntext和圖像數據類型不能比較或排序，使用IS NULL時除外或LIKE運營商。

我基本上是想從每個賬戶最高message_no，我想讓它顯示了message_text，但它不會允許它，因爲它是一個text數據類型。

Answer 1

TEXT，NTEXT和IMAGE被棄用，應該由對應類型VARCHAR(MAX)，NVARCHAR(MAX)和VARBINARY(MAX)代替。你可能會投你TEXT -column與

CAST(t1.message_text AS VARCHAR(MAX)) 

可能足以在你的子選擇，一旦做到這一點：

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

你不能比較文字，圖片，types..If你的數據要使用它們，將它們更改爲varchar或nvarchar ..下面

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)) 

個參考文獻：
The text, ntext, and image data > types cannot be compared or sorted, except when using IS NULL or LIKE > operator