problem with join

hi, I have two tables join with each other,
key from table1 is nvarchar column, key from table2 is varchar column, so
when they join, the performance is very bad, however, when I change both
them to varchar and join them together, the performance is much better.
but the problem is I don't want to change the column definition, I still
want to improve the query. is it possible?When column datatypes are different in comparison side, SQL Server has to
internally convert it for you and that's why your query is performing slower
.
This is by design and is the expected.
You can use CAST funtion and see if it helps which I highly doubt.
"Britney" wrote:

> hi, I have two tables join with each other,
> key from table1 is nvarchar column, key from table2 is varchar column, s
o
> when they join, the performance is very bad, however, when I change both
> them to varchar and join them together, the performance is much better.
> but the problem is I don't want to change the column definition, I still
> want to improve the query. is it possible?
>
>