Question

this is a very weird issue.
I have 3 tables, all with key relations on agent_id.

Now this query :

select DATE_FORMAT(created_on,"%d/%m/%y") as date
from logs
where agent_id = "18"
and log_status="1"
and date_format(created_on,"%m/%y") = "12/12"
group by YEAR(created_on), MONTH(created_on), DAY(created_on) desc

Does exactly what it suppoused to, it returns 3 rows of :

date
31/12/12
30/12/12
26/12/12

However when I join 2 other tables it excludes the date of 31/12/12. This is the query :

select  DATE_FORMAT(l.created_on,"%d/%m/%y") as date
from logs l
join logs_rewards lr on l.id = lr.related_log_id 
join agents a on a.id = l.agent_id 
where l.log_status = "1" 
and DATE_FORMAT(l.created_on,"%m/%y") = '12/12'
AND l.agent_id = '18' 
group by YEAR(l.created_on), MONTH(l.created_on), DAY(l.created_on) desc

This returns :

date
30/12/12
26/12/12

And I can’t figure out why that happens. Any help?

I’ve tried changing AND l.agent_id = '18' to AND a.id = '18' but same result.

Answer 1

This is because data are not mapped in all the 3 tables.

Below query will work

select  DATE_FORMAT(l.created_on,"%d/%m/%y") as date
from logs l
left join logs_rewards lr on l.id = lr.related_log_id 
left join agents a on a.id = l.agent_id 
where l.log_status = "1" 
and DATE_FORMAT(l.created_on,"%m/%y") = '12/12'
AND l.agent_id = '18' 
group by YEAR(l.created_on), MONTH(l.created_on), DAY(l.created_on) desc