SQL complicated sql query

Question

Imagine this tables:

| USER |
|------|
| _id  |

| PHOTO |
|-------|
|  _id  |
|  user | - who uploaded it

| RATING |
|--------|
| user   | - who vote
| photo  | - for which foto

And then I need to extract All photos uploaded by $user And on top of that, what rating the photo has...

for example:

USER
1

PHOTO
50    |    1
51    |    1
52    |    1

RATING
2     |    50
3     |    51
2     |    51
2     |    52
4     |    51
3     |    50

My Expected result for function get_info($id):

$id = 1;

result:
_id   |  rating
50    |    2
51    |    3
52    |    1

Is there possible one task sql ? thanks

Answer 1

Use join and count with group by

select p._id,count(distinct r.user)
from photo p
join rating r on(p._id=r.photo)
where p.user = 1
group by p._id

Since your photo table has an association with rating table as _id is related to the photo column of rating table so join them, then count each distinct user for each photo

Demo