Month average

Question

I would really like to make a query (I think that is the right word) to determine the average number of sales for each month (for example, Jan thru Dec). Not the average number of per month!
I have a table as follows:
CREATE TABLE sale
id               VARCHAR2(32)     NOT NULL,
item               VARCHAR2(32)     NOT NULL,
saledate          DATE,
PRIMARY KEY(id),
Populated with data like:
001 AAA 08-FEB-00
002 ZZZ 14-MAR-01
003 HHH 06-OCT-02
004 DDD 30-MAR-03
005 KKK 12-APR-03
006 GGG 22-SEP-04
007 BBB 15-MAR-04
008 BBB 16-MAR-04
009 SSS 17-MAR-04
010 SSS 18-MAR-04
011 BBB 19-MAR-04
I did manage to create the below query which returns the average sales per month but this is NOT want I wish for:
SELECT AVG(TOTAL)
FROM (SELECT MONTH, COUNT(MONTH) as TOTAL
FROM (SELECT TO_CHAR(saledate, 'MON') as MONTH from sale)
GROUP BY MONTH);
I would like an average output per month, example:
JAN     0
FEB     0
MAR     2
DEC     0
I have no idea...
Thanks...

Answer 1

Okay, you want the average of the monthly sales. You can get that by doing this:
SELECT to_char(x.month, 'MON') AS month, avg(mon_tot) AS avg
FROM   ( SELECT trunc(month, 'MM') AS month, count(*) AS mon_tot
         FROM   sales
         GROUP  BY trunc(month, 'MM') x
GROUP BY to_char(x.month, 'MON');Now your other problem is filling in the gaps for months where there are no sales. You will find Help Required for date display & mutating trigger to be helpful if you are using Oracle9i or higher, otherwise you will need to use Justin's variation.
Cheers, APC