Question

SELECT * FROM TableA
INNER JOIN TableB
ON TableA.name = TableB.name

SELECT * FROM TableA, TableB
where TableA.name = TableB.name

Which is the preferred way and why?
Will there be any performance difference when keywords like JOIN is used?

Thanks

Answer 1

The second way is the classical way of doing it, from before the join keyword existed.

Normally the query processor generates the same database operations from the two queries, so there would be no difference in performance.

Using join better describes what you are doing in the query. If you have many joins, it’s also better because the joined table and it’s condition are beside each other, instead of putting all tables in one place and all conditions in another.

Another aspect is that it’s easier to do an unbounded join by mistake using the second way, resulting in a cross join containing all combinations from the two tables.