Question

I have a NVARCHAR(max) column in a table and a stored procedure that would update this column as well as any other column in the table using CASE switching:

CREATE PROCEDURE updateTable
   @columnName sysname,
   @value nvarchar(max)
AS 
   UPDATE [dbo].[TestTable]
   SET 
      BigNvarcharValue = CASE @columnName WHEN 'BigNvarcharValue' THEN @value ELSE BigNvarcharValue END,  
      TableName = CASE @columnName WHEN 'TableName' THEN @value ELSE TableName END

All is good if I execute this procedure from SQL Management Studio with

EXEC [dbo].[updateTable]
     @columnName = 'BigNvarcharValue',
     @value = N'SOME BIG 80Kb value'

I can also update TableName from C# code using the same stored procedure, but when it comes to updating this BigNvarcharValue from C#, it fails with SQLException that “String or binary data would be truncated”. Now, I figured it has something to do with CASE in this stored procedure, because when I break it to a simpler stored procedure, everything works fine:

CREATE PROCEDURE updateTable   
     @columnName sysname,   
     @value nvarchar(max)
AS       
   UPDATE [dbo].[TestTable]   
   SET BigNvarcharValue=@value

I read a bunch of forum posts that describe this problem of trying to insert a bigger value into NVARCHAR column that would cause this exception, but it doesnt seem to apply.

I’m fairly new to T-SQL, so are there any limitations of CASE that I dont know of?

P.S. BigNvarcharValue is NVARCHAR(MAX) and TableName is NVARCHAR(50)

Answer 1

What are the data types of the columns you’re dealing with? Because I’ve reproduced the error by attempting to insert a value that is allowed by NVARCHAR(max) into a column that is VARCHAR(50).

To reiterate – NVARCHAR(max) is allowing you to specify a value that is longer than the stated data type, which is why you get the error about truncation.