unicode for database - best for overall performance?

i read in the below:

"ll modern operating systems and development platforms use Unicode internally. By using nvarchar rather than varchar, you can avoid doing encoding conversions every time you read from or write to the database. Conversions take time, and are prone to errors. And recovery from conversion errors is a non-trivial problem.

If you are interfacing with an application that uses only ASCII, I would still recommend using Unicode in the database. The OS and database collation algorithms will work better with Unicode. Unicode avoids conversion problems when interfacing with other systems. And you will be preparing for the future. And you can always validate that your data is restricted to 7-bit ASCII for whatever legacy system you're having to maintain, even while enjoying some of the benefits of full Unicode storage.

Can you qualify that if it is safe to allow nvarchar even when unicode is not used in the application, but may be better for overall system?

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lcohanDatabase AnalystCommented:
I would definitely NOT recommend to use N-char/varchar/text if not needed. For instance SQL may not use an index even if exists and matching the WHERE clauses IF you miss the N in front of a string to search and that could be serious performance issue that can be fixed ONLY by adding that little missing N in front of all strings in a where clause. Speciffic - I work with a 3rd party product where we had this EXACT issue and when we proved it to the vendor...they'll have a lots of changes to make just because they used N for all text like fields in the database - just in case to be safe if anyone puts a UNICODE char. well...is their app and they should not allow it to happen.

Anyway you could do a quick test based on my comments to prove it for yourself.

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