Dave62 (1/7/2010)
I can understand the confusion with this question since msdn refers to IN many different ways. A number of msdn links have already been posted to defend different answers and here is another one.http://msdn.microsoft.com/en-us/library/ms177682.aspx
In the remarks section the first sentence refers to IN as a clause. "...values (many thousands) in an IN clause can..."
Also, the article referenced is specifically for IN (Transact-SQL) not predicates or logical operators.
Dave
Well yet another term - see here for details with regards to the "logical" IN clause.
http://www.articleworld.org/index.php/Clause_%28logic%29
Edit: Just to provide an example, the IN clause in predicate
Edit2: added operator to IN clause
fieldx IN (1,2,3)
is
IN (1,2,3)
Not to mix up with "grammar" clauses like the SELECT or FROM clause.
Best Regards,
Chris Büttner