CASE WHEN with ORM (SQLalchemy)

Question

I am using SQLAlchemy with the ORM paragdim. I don\'t manage to find a way to do a CASE WHEN instruction. I don\'t find info about this on the web.

Is it possible ?

Answer 1

I got this to work with an aggregate function, in this case func.sum

My Example Code

from sqlalchemy import func, case

my_case_stmt = case(
    [
        (MyTable.hit_type.in_(['easy', 'medium']), 1),
        (MyTable.hit_type == 'hard', 3)
    ]
)

score = db.session.query(
    func.sum(my_case_stmt)
).filter(
    MyTable.success == 1
)

return score.scalar()

My Use Case

MyTable looks like this:

|   hit_type     |  success |  
-----------------------------  
|   easy         |   1      |  
|   medium       |   1      |  
|   easy         |   0      |  
|   hard         |   1      |  
|   easy         |   0      |
|   easy         |   1      |  
|   medium       |   1      |  
|   hard         |   1      |

score is computed as such: score = num_easy_hits + num_medium_hits + (3 * num_hard_hits)

4 successful easy/medium hits and 2 successful hard hits gives you (4 + (2*3)) = 10