Question

What the difference between the 2 queries below

UPDATE

This question is already answered in a similar question here LEFT JOIN vs. LEFT OUTER JOIN in SQL Server.

SELECT * FROM ca 
LEFT JOIN exam 
ON ca.subject = exam.subject

and

SELECT * FROM ca 
LEFT OUTER JOIN exam 
ON ca.subject = exam.subject

Tables

Table 'CA'
--------------------
subject|score
----------------
ENG    |25
MTH    |34
BIO    |18


Table 'Exam'
--------------------
subject|score
----------------
ENG    |25

Running the 2 queries produce the same result in mysql, sqlserver 2008. I didn’t test in Oracle.

subject | score1 | subject | score1
--------------------------------------
ENG       14       ENG       44
MTH       28       NULL      NULL
BIO       22       NULL      NULL

What’s the purpose of that OUTER clause

Answer 1

There is no difference. The OUTER keyword is optional.