Why Does Nvarchar(Max) in T-SQL Truncate to 4000 Characters?

Truncation in Nvarchar(Max) to 4000 Characters in TSQL

This issue arises when attempting to store large chunks of text in a variable declared as Nvarchar(Max) in TSQL. Surprisingly, the variable only accommodates 4000 characters instead of the expected 8000.

The explanation lies in the nature of datatype assignment in TSQL. Declaring a variable as Nvarchar(Max) does not automatically confer the Max attribute. Instead, the variable initially behaves as a collection of smaller (less than 4000 character) string constants. When these constants are concatenated together, the resulting @SQL1 variable still has a character limit of 4000.

To resolve this issue, ensure that the right-hand side of the assignment statement for @SQL1 is already an Nvarchar(Max) variable. This will guarantee that the resulting value is stored with the maximum allowable character limit.

For example, the following code will correctly assign the Nvarchar(Max) data type to @SQL1 from the beginning:

SET @SQL1 = NVARCHAR(Max)
SET @SQL1 = @SQL1 + 'SELECT DISTINCT VenueInfo.VenueID, VenueInfo.VenueName...

This approach prevents integer division behavior, where data types are inferred based on the precedence of operators. In this case, the precedence of assignment is always last, similar to other programming languages. Therefore, the assignment above treats the entire string as Nvarchar(Max) from the outset.

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