Question

I’m building my query using the advice from Does ORMLITE support SQL EXISTS?

public List<Crag> getAllCragsWithLocation() {
    QueryBuilder<Crag, Integer> cragQueryBuilder = _helper.getCragDao().queryBuilder();
    QueryBuilder<CragLocation, Integer> cragLocationQueryBuilder = _helper.getCragLocationDao().queryBuilder();
        try {
            cragLocationQueryBuilder.where().eq("locationType", 0);
            cragQueryBuilder.where().exists(cragLocationQueryBuilder);
            return cragQueryBuilder.query();
        } catch (Exception e) {
            Log.e(TAG,e.toString());
            return new ArrayList<Crag>();
        } 
}

This returns all crags regardless of if they have a cragLocation so long as there are any cragLocation with a locationType of 0. Which is understandable…

In the example linked above…

QueryBuilder<Visit, Integer> visitQb = visitDao.queryBuilder();
visitQb.where().eq(Visit.CLIENT_ID_FIELD, client.getId());
QueryBuilder<Client, Integer> clientQb = clientDao.queryBuilder();
clientQb.where().exists(visitQb);
List<Client> results = clientQb.query();

I guess the query is linking to the id of a specific client or perhaps more clearly

select * from client c
    where EXISTS (select * from visit v where c._id = v.client_id)

in my case

select * from Crag c
    where EXISTS (select * from CragLocation cl where c.id = cl.crag_id)

So my final query would be:

select * from Crag c
    where EXISTS (select * from CragLocation cl where c.id = cl.crag_id and cl.location_type = 0)

Answer 1

I don’t think you want to be using SQL EXISTS here. The query that ORMLite is going to generate does not include any special WHERE clause — it’s not that smart.

cragLocationQueryBuilder.where().eq("locationType", 0);
cragQueryBuilder.where().exists(cragLocationQueryBuilder);

This query means that if the there are any locations where locationType == 0 then it will return all of the Crag entries.

I would recommend that you use the where().in(QueryBuilder) method. This way you can return the crags that have a location whose type is 0.

cragLocationQueryBuilder.selectColumns("crag_id).where().eq("locationType", 0);
cragQueryBuilder.where().in("id", cragLocationQueryBuilder);

This will generate a SQL query something like:

select * from Crag
    where id IN (select crag_id from CragLocation cl.location_type = 0)