Character set mismatch

Question

Hi All, I have a SQL statement like this:

SELECT 
  a.ColumnA, b.ColumnB || 
 CASE WHEN TRIM(c.ColumnC) IS NOT NULL THEN ' (' || c.ColumnC || ')' ELSE '' END AS ClassName
 FROM TableA a INNER JOIN TableB b ON a.SomeColumn = b.SomeColumn 
 INNER JOIN TableC c on a.SomeCol = c.SomeCol

I'm getting an error "Character set mismatch" at the " ELSE '' " part of the CASE expression. Can someone suggest where I'm doing it wrong? Thank you.

Answer 1

Did you try replacing '' with NULL? Also, try removing ELSE part altogether because it will return NULL anyway.

Answer 2

You cannot concatenate VARCHAR and NVARCHAR values without a CAST statement.