Query to get all guests attending per date

Question

First I want to confirm this is even a sound and correct query.
Second I want to join in a way where even dates where no guests are attending shows up:

I want to get all screening dates where location = "Studio" , There are 5 dates that have location Studio, so I expect 5 results. But I only get 4 because only 4 days have guests attending. How do I rewrite my query to show days where no guests are attending too (fifth row)

SCHEMA

screening_date_guest(guest_id, screening_date_id, attending) 
user_guest_group(guest_id, user_id, group_id) 

NOTES

• a guest can belong to only one group_id but to multiple user_id's
• attending is a boolean

Query

select 
    count(distinct(sdg.guest_id)),
    `date`
from 
    screening_date_guest sdg 
inner join 
    user_guest_group ugs on ugs.guest_id = sdg.guest_id
inner join 
    screening_dates sd on sd.id = sdg.screening_date_id
where 
    attending = 1
AND 
    sd.location = 'Studio'
group by 
    `date`
order by sd.`date`

My current RS looks like:

15, 2015-05-18 00:00:00
4,  2015-05-19 00:00:00
2,  2015-05-20 00:00:00
4,  2015-05-21 00:00:00

There should be another row:

5,  2015-05-22 00:00:00

I tried doing left joins, but still end up getting 4 rows.

Answer 1

I think you want a right join on the screening_dates table:

http://www.w3schools.com/sql/sql_join_right.asp

select 
    count(distinct(sdg.guest_id)),
    `date`
from 
    screening_date_guest sdg 
inner join 
    user_guest_group ugs on ugs.guest_id = sdg.guest_id
right join 
    screening_dates sd on sd.id = sdg.screening_date_id
where 
    attending = 1
AND 
    sd.location = 'Studio'
group by 
    `date`
order by sd.`date`

Answer 2

If you want to get the fifth user who is not attending then you simply need to remove the attending column from your where condition ie, attending = 1

select 
    count(distinct(sdg.guest_id)),
    `date`
from 
    screening_date_guest sdg 
inner join 
    user_guest_group ugs on ugs.guest_id = sdg.guest_id
inner join 
    screening_dates sd on sd.id = sdg.screening_date_id
where 
    sd.location = 'Studio'
group by 
    `date`
order by sd.`date`

Answer 3

Try this

select case when attending = 1
then count(distinct(sdg.guest_id))
else
'0'
end ,
    `date`
from 
    screening_date_guest sdg 
inner join 
    user_guest_group ugs on ugs.guest_id = sdg.guest_id
inner join 
    screening_dates sd on sd.id = sdg.screening_date_id
where 
    sd.location = 'Studio'
group by 
    `date`,attending
order by sd.`date`

Answer 4

This should give you all 5 days:

select 
    count(distinct(sdg.guest_id)),
    sd.'date'
  from 
    screening_dates sd
  left join 
    screening_date_guest sdg 
        on sdg.screening_date_id = sd.id 
       and sdg.attending = 1
  where sd.location = 'Studio'

I don't see why you need to include the user_guest_group table.