Question

Say for example, I have the following two tables:

TableA { _id }
TableB { _id, TableA_id, OptionString }

Each row in TableA has one or more rows in TableB referencing it (using the TableA_id foreign key).

My query lists rows in TableA to display to the user.

OptionString can be one of two values – let’s say “Option1” and “Option2”.

Now I want the query to still list rows in TableA, but I want to provide the user with a filter to say “only display rows in TableA where the OptionString has either “Option1” OR “Option2” (ie. exclusive or).

I’ve tried using COUNT, but the problem is that a zero count displays no results (not ‘0’ as I would want).

I’m sure I must be missing something simple with this.

Any help would be greatly appreciated.

Cheers,
Dan.

Answer 1

Try this, if I understand your question correctly

select a._id
from tableA a
join tableB b on a._id=b.tableA_id
where b.optionString in ('Option1','Option2')
group by a._id
having count(*)=1

Revised query based on new information

select a._id
from tableA a
join (select distinct _id,tablea_id,optionString from TableB) b 
        on a._id=b.tableA_id
where b.optionString in ('Option1','Option2')
group by a._id
having count(*)=1

What I am doing here is forcing distinct values from tableB