Inner join vs Where

Question

Is there a difference in performance (in oracle) between

Select * from Table1 T1 
Inner Join Table2 T2 On T1.ID = T2.ID

And

Answer 1

I don't know about Oracle but I know that the old syntax is being deprecated in SQL Server and will disappear eventually. Before I used that old syntax in a new query I would check what Oracle plans to do with it.

I prefer the newer syntax rather than the mixing of the join criteria with other needed where conditions. In the newer syntax it is much clearer what creates the join and what other conditions are being applied. Not really a big problem in a short query like this, but it gets much more confusing when you have a more complex query. Since people learn on the basic queries, I would tend to prefer people learn to use the join syntax before they need it in a complex query.

And again I don't know Oracle specifically, but I know the SQL Server version of the old style left join is flawed even in SQL Server 2000 and gives inconsistent results (sometimes a left join sometimes a cross join), so it should never be used. Hopefully Oracle doesn't suffer the same issue, but certainly left and right joins can be mcuh harder to properly express in the old syntax.

Plus it has been my experience (and of course this is strictly a personal opinion, you may have differnt experience) that developers who use the ANSII standard joins tend to have a better understanding of what a join is and what it means in terms of getting data out of the database. I belive that is becasue most of the people with good database understanding tend to write more complex queries and those seem to me to be far easier to maintain using the ANSII Standard than the old style.