Will joining on integer be quicker than joining on nvarchar?

Question

Does it have a significant impact on performance if you use integer key columns instead of nvarchar(20) ? I assume that all fields used in the joins have been indexed.

Answer 1

The INT should be faster than NVARCHAR(20) because an INT is only 4 bytes, so you can hold more indexes/data in memory at one time. You should always try to use the smallest data type practical for all columns.