Question

Is there a difference in performance (in oracle) between

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

And

Select * from Table1 T1, Table2 T2  Where T1.ID = T2.ID 

?

Answer 1

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