Why varchar is slower than nvarchar

Question

Possible duplicate:
varchar vs nvarchar

I changed the entire nvarchar column to varchar in the hope of speeding up the request. but my request is now slowing down. before he worked 15 seconds, now the working time is 26 seconds.

what can make it slower? am i avoiding something?

Answer 1

If you show us the schema and query, we can help - my first bet will be that you have different types of data in the schema and query, and therefore you are now doing an additional type conversion somewhere, There may also be consequences of the actual data conversion that you performed, your database may be more fragmented than it was (or, as suggested in response to another identical question that you asked, your statistics may be outdated, which leads to poor queries).