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

They should be exactly the same. However, as a coding practice, I would rather see the Join. It clearly articulates your intent,

Answer 2

Functionally they are the same as has been said. I agree though that doing the join is better for describing exactly what you want to do. Plenty of times I've thought I knew how I wanted to query something until I started doing the joins and realized I wanted to do a different query than the original one in my head.

Answer 3

They're both joins and where that do the same thing.

Give a look at In MySQL queries, why use join instead of where?

Answer 4

If the query optimizer is doing its job right, there should be no difference between those queries. They are just two ways to specify the same desired result.

Answer 5

No! The same execution plan, look at these two tables:

CREATE TABLE table1 (
  id INT,
  name VARCHAR(20)
);

CREATE TABLE table2 (
  id INT,
  name VARCHAR(20)
);

The execution plan for the query using the inner join:

-- with inner join

EXPLAIN PLAN FOR
SELECT * FROM table1 t1
INNER JOIN table2 t2 ON t1.id = t2.id;

SELECT *
FROM TABLE (DBMS_XPLAN.DISPLAY);

-- 0 select statement
-- 1 hash join (access("T1"."ID"="T2"."ID"))
-- 2 table access full table1
-- 3 table access full table2

And the execution plan for the query using a WHERE clause.

-- with where clause

EXPLAIN PLAN FOR
SELECT * FROM table1 t1, table2 t2
WHERE t1.id = t2.id;

SELECT *
FROM TABLE (DBMS_XPLAN.DISPLAY);

-- 0 select statement
-- 1 hash join (access("T1"."ID"="T2"."ID"))
-- 2 table access full table1
-- 3 table access full table2

Answer 6

Using JOIN makes the code easier to read, since it's self-explanatory.

There's no difference in speed(I have just tested it) and the execution plan is the same.