Can call a function in the select statement?

Question

Is there any ways to call a function in the select statement?
what I like to do is this:
select deptno, totalEmployees(deptno), TotalSalary(deptno)
from emp;
I know it can be done by count(*) and join tables, but my case
is much more complex and the where clauses are different from
one function to another, and have many tables to join and many
combinations
Thanks

Answer 1

Functions can be used in a select statement subject to certain
restrictions, see
http://otn.oracle.com/docs/products/oracle8i/doc_library/817_doc/
server.817/a85397/statem9b.htm#2062024
It's under "CREATE FUNCTION> Keywords and Parameters> function>
Restrictions on User-Defined Functions"
Here is an except...
When a function is called from within a query or DML statement,
the function cannot:
a) Have OUT or IN OUT parameters
b) Commit or roll back the current transaction, create or roll
back to a savepoint, or alter the session or the system. DDL
statements implicitly commit the current transaction, so a user-
defined function cannot execute any DDL statements.
c) Write to the database, if the function is being called from a
SELECT statement. However, a function called from a subquery in
a DML statement can write to the database.
d) Write to the same table that is being modified by the
statement from which the function is called, if the function is
called from a DML statement.
Except for the restriction on OUT and IN OUT parameters, Oracle
enforces these restrictions not only for the function called
directly from the SQL statement, but also for any functions that
function calls, and on any functions called from the SQL
statements executed by that function or any function it calls.