Question { 3631 }

What is the difference between referencing and joining?

Answer

referencing:

ex: table A--> having primary key
table B--> having foreign key. now referencing means
this table B refers table A using the particular field u
mentioned as primary key and foreign key.

joining:
we can perform joining operation only if two table
have primary key and foreign key relationship. using this
keys we can perform inner, left outer,fullouter,right outer
joins.

Question { 4144 }

mysql> select * from store;
+------+-------+-------+
| id | month | sales |
+------+-------+-------+
| 1 | 1 | 100 |
| 1 | 2 | 100 |
| 1 | 3 | 200 |
| 1 | 4 | 300 |
| 1 | 5 | NULL |
| 1 | 6 | 200 |
| 1 | 7 | 800 |
| 1 | 8 | 100 |
| 1 | 9 | 240 |
| 1 | 10 | 140 |
| 1 | 11 | 400 |
| 1 | 12 | 300 |
| 2 | 1 | 300 |
| 2 | 2 | 300 |
| 2 | 3 | 300 |
| 2 | 4 | 200 |
| 2 | 5 | 200 |
| 2 | 6 | 200 |
| 2 | 7 | 100 |
| 2 | 8 | 100 |
| 2 | 9 | 300 |
| 2 | 10 | 100 |
| 2 | 11 | 150 |
| 2 | 12 | 150 |
+------+-------+-------+

this is my table. i need to display output like this.

+------+----------+----------+----------+----------+
| id | quarter1 | quarter2 | quarter3 | quarter4 |
+------+----------+----------+----------+----------+
| 1 | 400 | 500 | 1140 | 840 |
| 2 | 900 | 600 | 500 | 400 |
+------+----------+----------+----------+----------+

what single query i have to write for this. i tried this
query and it displays like the below

mysql> select id,sum(sales) as quarter1,(select sum(sales)
from store where mont
h>3 and month<7 ) as quarter2,(select sum(sales) from store
where month>6 and mo
nth<10)as quarter3 from store where month>0 and month<4
group by id;
+------+----------+----------+----------+
| id | quarter1 | quarter2 | quarter3 |
+------+----------+----------+----------+
| 1 | 400 | 1100 | 1640 |
| 2 | 900 | 1100 | 1640 |
+------+----------+----------+----------+
2 rows in set (0.00 sec)

tel me how to rectify it.

Answer

try this also my dear friend and thanks for ur answer too
select s.id,
sum(sales),
(select sum(sales)from store a where month in(1,2,3) and
a.id=s.id)as q1,
(select sum(sales)from store b where month in(4,5,6) and
b.id=s.id)as q2,
(select sum(sales)from store c where month in(7,8,9) and
c.id=s.id)as q3,
(select sum(sales)from store d where month in(10,11,12)
and d.id=s.id)as q4
from store s group by id;