Why is my NVARCHAR(MAX) variable in T-SQL only holding 4000 characters?

Why am I Only Getting 4000 Characters Instead of 8000 for Nvarchar(Max) in TSQL?

In your SQL query, you've declared the variable @SQL1 as NVARCHAR(Max) but are facing an issue where it's only storing 4000 characters. This happens because of a subtle behavior in TSQL regarding the automatic conversion of data types during concatenation.

Understanding the Issue:

• When you declare @SQL1 as NVARCHAR(Max), it has the capacity to hold 2GB of data. However, its datatype is not actually NVARCHAR(Max) until you assign a value to it.
• Before assignment, @SQL1 is essentially a collection of strings, each shorter than 4000 characters (in your case, the constants in your query).
• When you concatenate these short strings with short variables, the resulting datatype remains as NVARCHAR(4000) because each operation involves strings that are less than 4000 characters long.
• Consequently, when you eventually assign the result to @SQL1, the datatype remains NVARCHAR(4000), and you end up with only 4000 characters.

Solution:

To ensure that @SQL1 becomes NVARCHAR(Max), you need to make sure that the data you are concatenating on the right-hand side is also NVARCHAR(Max). One way to do this is by explicitly casting any constants or variables to NVARCHAR(Max) before concatenation.

For example, the following code will correctly result in @SQL1 being NVARCHAR(Max):

SET @SQL1 = N'';
SET @SQL1 = @SQL1 + CAST('SELECT DISTINCT Venue...,' AS NVARCHAR(MAX));

This ensures that the SELECT statement is concatenated with a string that has the NVARCHAR(Max) datatype, forcing the result to also be NVARCHAR(Max).

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