CODEWITHSUNDEEP
mysql
Kumar
Kumar

Reputation: 355

get average value depending on month?

My table:

rating   date
   4    12/02/2013
   3    12/02/2013
  2.5   12/01/2013
   3    12/01/2013
  4.5   21/11/2012
   5    10/11/2012

If I give input as 3 the last three months (02,01,12), average of rating result should come

I tried by using GROUP BY but I get this result:

 rating   month
  3.5      02
 2.75      01

For the 12th month no rating so no output.....

My desired result:

 rating   month
  3.5      02
 2.75      01
   0       12

Upvotes: 0

Views: 110

Answers (2)

जलजनक
जलजनक

Reputation: 3071

SELECT coalesce(avg(rating), 0.0) avg_rating, req_month
  FROM    yourTable
       RIGHT JOIN
          (SELECT month(now()) AS req_month
           UNION
           SELECT month(now() - INTERVAL 1 MONTH) AS req_month
           UNION
           SELECT month(now() - INTERVAL 2 MONTH) AS req_month) tmpView
       ON month(yourTable.date) = tmpView.req_month
 WHERE    yourTable.date > (  (curdate() - INTERVAL day(curdate()) - 1 DAY) - INTERVAL 2 MONTH)
  OR ratings.datetime IS NULL
GROUP BY month(yourTable.date);

Upvotes: 2

Taryn
Taryn

Reputation: 247680

The problem is that you want to return months that do not exist. If you do not have a calendar table with dates, then you will want to use something like the following:

select d.mth Month,
  coalesce(avg(t.rating), 0) Rating
from 
(
  select 1 mth union all
  select 2 mth union all
  select 3 mth union all
  select 4 mth union all
  select 5 mth union all
  select 6 mth union all
  select 7 mth union all
  select 8 mth union all
  select 9 mth union all
  select 10 mth union all
  select 11 mth union all
  select 12 mth 
) d
left join yourtable t
  on d.mth = month(t.date)
where d.mth in (1, 2, 12)
group by d.mth

See SQL Fiddle with Demo

Upvotes: 3

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