Some understanding about joins

[tawright915]

Can someone please help me in understanding inner and outer joins? I
seem to have a block when it comes to understanding this concept.

And please if you have nothing helpful to contribute then please do not
reply.

Thanks
Tom

[Charles Hooper]

Short answer:
* Inner join - the value must be in BOTH tables
* Outer join - the value must be in at least ONE table

Assume that the following table and columns in those tables, and data
in those columns exist:
TABLE_1.ANIMAL
COW
PIG
ZEBRA
SHARK
ROOSTER
LION

TABLE_2.ANIMAL
COW
PIG
DOG

TABLE_3.ANIMAL
ZEBRA
LION
TIGER

Inner join TABLE_2 and TABLE_3
SELECT
T2.ANIMAL,
T3.ANIMAL
FROM
TABLE_2 T2,
TABLE_3 T3
WHERE
T2.ANIMAL=T3.ANIMAL;

(no results)
-------------------

(Left) Outer join TABLE_2 and TABLE_3, include all rows from TABLE_2
SELECT
T2.ANIMAL,
T3.ANIMAL
FROM
TABLE_2 T2,
TABLE_3 T3
WHERE
T2.ANIMAL=T3.ANIMAL(+);

T2.ANIMAL T3.ANIMAL
COW (null)
PIG (null)
DOG (null)
-------------------

Inner join TABLE_1 and TABLE_2
SELECT
T1.ANIMAL,
T2.ANIMAL
FROM
TABLE_1 T1,
TABLE_2 T2
WHERE
T1.ANIMAL=T2.ANIMAL;

TABLE_1.ANIMAL TABLE_2.ANIMAL
COW COW
PIG PIG
-------------------

(Right) Outer join TABLE_1 and TABLE_2, include all rows from TABLE_2
SELECT
T1.ANIMAL,
T2.ANIMAL
FROM
TABLE_1 T1,
TABLE_2 T2
WHERE
T1.ANIMAL(+)=T2.ANIMAL;

TABLE_1.ANIMAL TABLE_2.ANIMAL
COW COW
PIG PIG
(null) DOG
-------------------

(One Method, Full) Outer join TABLE_1 and TABLE_2, include all rows
SELECT
T1.ANIMAL,
T2.ANIMAL
FROM
TABLE_1 T1,
TABLE_2 T2
WHERE
T1.ANIMAL(+)=T2.ANIMAL
UNION
SELECT
T1.ANIMAL,
T2.ANIMAL
FROM
TABLE_1 T1,
TABLE_2 T2
WHERE
T1.ANIMAL=T2.ANIMAL(+);

TABLE_1.ANIMAL TABLE_2.ANIMAL
COW COW
PIG PIG
(null) DOG
ZEBRA (null)
SHARK (null)
ROOSTER (null)
LION (null)

Charles Hooper
PC Support Specialist
K&M Machine-Fabricating, Inc.

[tawright915]

Thank you so much. The light went on.

[juan....@gmail.com]

There's a good discussion at http://en.wikipedia.org/wiki/Join_(SQL)

[ExpertDba]

Charles Hooper,

Beautifully put answer!

regards,
Channesh

[siva]

Thanks Charles Hooper,

its really a nice reply it helped me to get out of the confusion
between the both

thanking you once again

regards

siva.