SQL fundamental question '!=' vs '<>' vs 'Not' [duplicate]

Question

Possible Duplicate:
Testing for inequality in T-SQL

Hi,

does there any different to use the '!=' vs '<>' vs 'Not'?

which one will have the worst performance

or it exist just because of the backward compatibility syntax?

Answer 1

• NOT does not always act the same
• != or <> are identical, no deprecation mentioned. <> is ISO though

Answer 2

AFAIK, if you want to check for NULL, you must use IS NOT and not != or <>