Sql Server int vs nvarchar comparison on performance?

Question

For you database design/performance gurus out there.

I\'m designing a table, I have the choice of either use int or nvarchar (128) for a column, assume space is not

Answer 1

Space is always a problem in databases. Wider keys mean less entries per page, more pages scanned to aggregate and sum values, means more IO, less performance. For clustered indexes, this problem gets multiplied by each non-clustered index, as they have to reproduce the lookup key (clustered key) in their leafs. So a key of type nvarchar(128) will almost always be worse than an INT.

On the other hand, don't use an INT key if is not appropriate. Always use the appropriate key, considering your queries. If you always going to query by an nvarchar(128) column value, then is possibly a good clustered key candidate. If you're going to aggregate by the nvarchar(128) key, then is likely a good clustered key candidate.