Question

i have one table name as a_ad_display with following column

displayId | campaignId | displaytime(date)

1          |    2      | 2012-12-19 12:41:08
2          |    2      | 2012-12-19 01:41:08
3          |    1      | 2012-12-20 10:41:08
4          |    1      | 2012-12-20 02:41:08
5          |    1      | 2012-12-21 12:41:08
6          |    2      | 2012-12-21 01:41:08
7          |    1      | 2012-12-21 12:41:08
8          |    1      | 2012-12-21 02:41:08

there is a multiple entry with same campaignId should be there.now what i want is to first of all fetch the campaignId with the highest count in a_ad_display and for that campaignId i want to get total number of count within the date

eg..from above table i have 1 number campaignId with highest row count

so for 1 number campaignId i want to display records like this..

        **Date**     | **countPerDay**
 2012-12-19          |      0
 2012-12-20          |      2
 2012-12-21          |      3

how can i achieve this in mysql database…hope anyone can guide me…

Answer 1

You can use this query

select 
    count(campaignId) as TCount,
    DATE(displayTime) as `Date`
from a_ad_display
where campaignId = 1
group by DATE(displayTime)

Although it will not display 0.

EDIT :

OK This is modified and fetches your result.

select
  date(a.displayTime) as `DisplayTime`,
  ifnull(l.TCount,0) as TCount
from a_ad_display as a
  left join (select
           count(campaignId) as TCount,
           displayTime
         from a_ad_display
         where campaignId = 1
         group by DATE(displayTime)) as l
    on date(a.displayTime) = date(l.displayTime)
group by DATE(a.displayTime)

Demo

MORE EDITS :

select
  date(a.displayTime) as `DisplayTime`,
  ifnull(l.TCount,0) as TCount
from a_ad_display as a
  left join (select
           count(campaignId) as TCount,
           displayTime
         from a_ad_display
         where campaignId = 1
         group by DATE(displayTime)) as l
    on date(a.displayTime) = date(l.displayTime)
group by DATE(a.displayTime)
order by a.displaytime desc limit 5

This is how you can select latest 5 records. If you want to select the latest campaign you can use a subquery instead of 1 take a look at this query

select
  date(a.displayTime) as `DisplayTime`,
  ifnull(l.TCount,0) as TCount
from a_ad_display as a
  left join (select
       count(campaignId) as TCount,
       displayTime
     from a_ad_display
     where campaignId = (select  campaignId from a_ad_display group by campaignId order by count(campaignId) desc limit 1)
     group by DATE(displayTime)) as l
    on date(a.displayTime) = date(l.displayTime)
group by DATE(a.displayTime)

EDITS :

I have edited the query this will fetch higher occurance campaignId and fetch results accordingly

Demo