将NTEXT列与常量值进行比较的正确方法是什么？

Question

If I use something like

[ntext2] <> '1,032.5',

I get this error:

The data types ntext and varchar are incompatible in the not equal to operator.

The best possible solution would be if comparison is implemented in the same way for any column type. (<> operator is applicable for both NVARCHAR and INT).

Answer 1

The ntext data type is deprecated in favour of the nvarchar(max) data type. If you can change the data type in the table, that would be the best solution. Then there is no problem comparing it to a varchar literal.

Otherwise you would have to cast the value before comparing it:

cast([ntext2] as nvarchar(max)) <> '1,032.5'

You might also consider using a nvarchar literal, which solves some similar data type problems:

cast([ntext2] as nvarchar(max)) <> N'1,032.5'

Answer 2

If you would prefer not to cast, you can get by in some scenarios using LIKE or PATINDEX , as demonstrated on this MSDN thread: http://social.msdn.microsoft.com/Forums/en-US/transactsql/thread/6bd4c661-ea0b-435f-af78-097e61549d41

The LIKE expression, without wildcards, would be (in this case) roughly equivalent to a test for equality.

In this case, the expression would be:

[ntext2] NOT LIKE '1,032.5'