Wsrtjtyk

Consider the following:

1. Family has_many kids (Family 1:many Kid)


2. Kid has an enum attribute age_group which can be baby, child, teenager, or adult

I would like to create several scopes:

1. Select all the families that have kids that are ONLY age_group: baby. What this mean is that if a family has a baby and a child, that family should not qualify for this scope.




2. Select all families that have a baby and child, but no teenager or adult.

The other scopes are age_group ONLY child, teenager, adult, etc. but I believe I can create that off the same logic as the 1st scope.

I ended up coming up with something like this...

Family.find_by_sql("SELECT * FROM kids WHERE NOT EXISTS ( SELECT NULL FROM kids WHERE kids.family_id = family.id AND family.age_group != 'baby')")

This seemed to get all the families with only babies in my limited test data. I didn't extensively test this however because it wasn't extendable. Since I had to use find_by_sql, I could not chain this with other activerecord where calls or add pagination to this.

I decided to take the other route and make a family_stage column in family and anytime kids are updated or added to family to update family_stage. It makes querying everything much more straightforward and puts the processing on the side of updates.