Not sure what is the result of this right outer join - mysql

Question

Right outer join is similar to a Union of a venn diagram right?
I mean for A right outer Join B we should get all the rows of B and any matching rows in A.
For some reason I am confused with the following:
Assume table Orders:
mysql> select * from orders;
+------------+------------+---------+----------+---------+
| orderedon | name | partnum | quantity | remarks |
+------------+------------+---------+----------+---------+
| 1996-05-19 | TRUE-WHEEL | 76 | 3 | PAID |
| 1996-09-02 | TRUE-WHEEL | 10 | 1 | PAID |
| 1996-06-30 | TRUE-WHEEL | 42 | 8 | PAID |
| 1996-06-30 | BIKE SPEC | 54 | 10 | PAID |
| 1996-05-30 | BIKE SPEC | 23 | 8 | PAID |
| 1996-01-17 | BIKE SPEC | 76 | 11 | PAID |
| 1996-01-17 | LE SHOPPE | 76 | 5 | PAID |
| 1996-06-01 | LE SHOPPE | 10 | 3 | PAID |
| 1996-06-01 | AAA BIKE | 10 | 1 | PAID |
| 1996-07-01 | AAA BIKE | 76 | 4 | PAID |
| 1996-07-01 | AAA BIKE | 46 | 14 | PAID |
| 1996-07-11 | JACKS BIKE | 76 | 14 | PAID |
| 1996-05-15 | TRUE-WHEEL | 23 | 6 | PAID |
| 1996-05-30 | BIKE SPEC | 20 | 2 | PAID |
+------------+------------+---------+----------+---------+
14 rows in set (0.00 sec)
and table Part:
mysql> select * from part;
+---------+---------------+---------+
| partnum | description | price |
+---------+---------------+---------+
| 54 | PEDALS | 54.25 |
| 42 | SEATS | 24.50 |
| 46 | TIRES | 15.25 |
| 23 | MOUNTAIN BIKE | 350.45 |
| 76 | ROAD BIKE | 530.00 |
| 10 | TANDEM | 1200.00 |
+---------+---------------+---------+
6 rows in set (0.00 sec)
I was expecting that the following query:
select p.partnum p_partnum,p.description p_desc,p.price p_price,o.name o_name,o.partnum o_partnum from part p right outer join orders o on o.partnum=54;
Would give me all the rows of Orders and just the rows of part that have partnum=54.
But I get this:
mysql> select p.partnum p_partnum,p.description p_desc,p.price p_price,o.name o_name,o.partnum o_partnum from part p right outer join orders o on o.partnum=54;
+-----------+---------------+---------+------------+-----------+
| p_partnum | p_desc | p_price | o_name | o_partnum |
+-----------+---------------+---------+------------+-----------+
| NULL | NULL | NULL | TRUE-WHEEL | 76 |
| NULL | NULL | NULL | TRUE-WHEEL | 10 |
| NULL | NULL | NULL | TRUE-WHEEL | 42 |
| 54 | PEDALS | 54.25 | BIKE SPEC | 54 |
| 42 | SEATS | 24.50 | BIKE SPEC | 54 |
| 46 | TIRES | 15.25 | BIKE SPEC | 54 |
| 23 | MOUNTAIN BIKE | 350.45 | BIKE SPEC | 54 |
| 76 | ROAD BIKE | 530.00 | BIKE SPEC | 54 |
| 10 | TANDEM | 1200.00 | BIKE SPEC | 54 |
| NULL | NULL | NULL | BIKE SPEC | 23 |
| NULL | NULL | NULL | BIKE SPEC | 76 |
| NULL | NULL | NULL | LE SHOPPE | 76 |
| NULL | NULL | NULL | LE SHOPPE | 10 |
| NULL | NULL | NULL | AAA BIKE | 10 |
| NULL | NULL | NULL | AAA BIKE | 76 |
| NULL | NULL | NULL | AAA BIKE | 46 |
| NULL | NULL | NULL | JACKS BIKE | 76 |
| NULL | NULL | NULL | TRUE-WHEEL | 23 |
| NULL | NULL | NULL | BIKE SPEC | 20 |
+-----------+---------------+---------+------------+-----------+
19 rows in set (0.00 sec)
Why am I getting the extra rows? Why does it combine the row of Order with partnum=54 to all rows of `part?

Answer 1

Your query is
select p.partnum p_partnum,p.description p_desc,p.price p_price,o.name o_name,o.partnum o_partnum
from part p right outer join orders o on o.partnum=54;
You are going for right join so even if there is no match in the joining table on the right side it will display records and it is happening in this case of your query
same is for left join there all the records of the table on the left side will be displayed even if they dont match
Refer http://www.w3schools.com/sql/sql_join_right.asp
For detailed explanation
Hope this helps

Answer 2

FROM part p
RIGHT OUTER JOIN orders o
ON o.partnum=54
...only has a condition on order, what you need to add is a condition that the part also corresponds to the order, or the database will consider any part a match;
FROM part p
RIGHT OUTER JOIN orders o
ON o.partnum=54
AND o.partnum = p.partnum
Of course, if you only want to show the rows where partnum=54, you're better off moving the o.partnum=54 to a WHERE condition instead. JOIN conditions are usually for connecting tables, WHERE usually for filtering.

Answer 3

Because you have RIGHT JOIN to orders with join condition partnum=54 you will get all rows from orders joined with parts when partnum=54. You have one row with partnum=54 and that row joined with all rows (cross join) from parts.

Answer 4

You're using o.partnum = 54 on ON condition, that's why you're getting extra rows
in your result.
You need to put the condition o.partnum = 54 on where clause.
How about this
select p.partnum p_partnum,p.description p_desc,p.price p_price,o.name o_name,o.partnum o_partnum
from part p right outer join orders o
on o.partnum = p.partnum
where o.partnum=54;
Edit : You may refer to this beautiful article how the result set gets disturb when you
put condition on ON clause and Where.