User Defined Function VS join - Performance....

Question

Hi All,
while linking the mulitple table and getting the values ....which one is the best ?
Joining or User defined function.....
single row function
select a.name , get_salary(empid) from emp a;
Note : get_salary function will return the salary from salary tables.
Using joins
select a.name ,b.salary from emp a, salary b
where a.empid=b.empid;
which is the performancewise best ?
also if you give any related document also fine.
Thanks in advance.
Edited by: BASKAR NATARAJAN on Jan 6, 2011 10:09 PM

Answer 1

Don't use such functions for joins. The function itself has to query the salary table. It will run the query against the salary table separately for each row that it reads from the emp table. You will end up with multiple recursive calls and possibly inconsistency in the output. (Imagine what would happen if the salary table were updated and commited while this query was running -- some rows would have been read with the pre-update values and others with the updated values).
Specifying the join in the query ensures that a single SQL call is executed and provides read consistency across all the rows it reads. And it is much faster, being one single parse and execute.
Hemant K Chitale
http://hemantoracledba.blogspot.com