Possible Duplicate:
Should I use != or <> for not equal in TSQL?
I see a number of questions using != to express the not equal operator in SQL.
Working mostly with SQL-Server and Oracle I usually prefer <> .
Are there DBMS which do not support <> ?
Edit:
SQL-Server even supports these 2-character operators with an embedded blank in between. I think that is from old Sybase days. I think no other DBMS followed them in this respect. And when you have to migrate your query to another DBMS it just becomes an error. Better don't use it.