I have one column that I recently converted to nvarchar(100) to store Asian characters. The other columns in this table, and the other tables in the same database, use varchar, int, bit and datetime. Since that change, some of my queries now take ten to twenty seconds to return less than fifty records. The tables store a thousand records or less.
I've read nvarchar has an associated IO performance cost with it, but this bad for such a small record set? Do I have to adopt an all or nothing approach with nvarchar (convert all varchar to nvarchar) or have I missed something obvious?