MySQL连续几天返回错误值

Question

I am trying to do a consecutive days count in mysql from a timestamp column. I thought I had this problem solved once long ago - but for some strange reason, it is returning the wrong value.

It should return a single column containing a username, the lowest date with the highest time value in the consecutive date list, and the largest number of consecutive days.

It all works except the largest number of consecutive days is not always correct.

SELECT username, day1, count(distinct date) days from (
    SELECT t1.username, t1.date, max(tmp.date) day1 from sites_surfed t1
        LEFT JOIN (
            SELECT tmp1.date from sites_surfed tmp1
            LEFT JOIN sites_surfed tmp2
                ON DATE_FORMAT(tmp1.date,'%d/%m/%Y') = DATE_FORMAT(tmp2.date,'%d/%m/%Y')+1
                AND tmp1.username = tmp2.username where (tmp1.username = 'viraladmin') 
                AND (tmp2.date is null))tmp on (t1.date >= tmp.date) where t1.username = 'viraladmin'
                GROUP BY t1.date
   ) fin  
   WEHERE username = 'viraladmin'
       GROUP BY day1 having count(distinct date) > 1 order by days

The below jsfiddle shows an example of it returning 3 for the total amount of consecutive days when it should only be return 2 as only two unique dates are in the table list

http://sqlfiddle.com/#!9/85f6d6/4

What is going on here and how do I fix this?

Answer 1

I've changed

GROUP BY t1.date

to

GROUP BY DATE_FORMAT(t1.date,'%d/%m/%Y')

This seems to be working.

SELECT username, day1, count(distinct date) days from (
    SELECT t1.username, t1.date, max(tmp.date) day1 from sites_surfed t1
        LEFT JOIN (
            SELECT tmp1.date from sites_surfed tmp1
            LEFT JOIN sites_surfed tmp2
                ON DATE_FORMAT(tmp1.date,'%d/%m/%Y') = DATE_FORMAT(tmp2.date,'%d/%m/%Y')+1
                AND tmp1.username = tmp2.username where (tmp1.username = 'viraladmin') 
                AND (tmp2.date is null))tmp on (t1.date >= tmp.date) where t1.username = 'viraladmin'
                GROUP BY DATE_FORMAT(t1.date,'%d/%m/%Y')
   ) fin  
   WHERE username = 'viraladmin'
       GROUP BY day1 having count(distinct date) > 1 order by days