Cannot compare or sort text, ntext, and image data types

Recently, when developing a file management system, I encountered a problem: the original local database is SQL2008, and there is a field SharedUserId of nvarchar(max) type, which is occasionally queriedSQL statement used...AND SharedUserId

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Microsoft Internet Explorer
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The text, ntext, and image data types cannot be compared or sorted unless the IS NULL or LIKE operators are used.(System.Exception)
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OK
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So, I even changed the local database field type to text, and then tested it, and a similar error was reported (even the SQL2008 is in English):

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Microsoft Internet Explorer
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The data types text and varchar are incompatible in the not equal to operator.(System.Exception)
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OK
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After searching on the Internet, the original query statement is slightly modified, and it works: ...AND SharedUserId replaced by ...AND DATALENGTH(SharedUserId) > 0 AND SharedUserIdIS NOT NULL