问题
I am really surprisde to see that in my MS SQL table, I am defining a field varchar and doing group by with another table's field.
When I do the same thing with the column as nvarchar it is 3 second faster than varchar
when, theoretically, varchar should be faster because of 1 byte char.
Can anyone explain me why nvarchar is faster in this instance?
Thanks in advance.
回答1:
Operating systems use Unicode internally. I think that makes nvarchar faster since it does not need any converting.
来源：https://stackoverflow.com/questions/6250728/nvarchar-perform-better-than-varchar