Joining from multiple tables using SQLAlchemy

Question

I think i am pretty close here, but maybe i need some pointers. I am trying to run the SQL query below in SQL Alchemy.

Endpoints for populating the UI with data. These need to consist of some joins.

select
    constraintid,
    sja.segment,
    sjs.source,
    sjct.constrainttype,
    constraintvalue,
    targeting,
    frequency,
    period
from signaljourneyaudienceconstraints
JOIN signaljourneyaudiences sja ON sja.audienceid = signaljourneyaudienceconstraints.audienceid;
JOIN signaljourneysources sjs ON sjs.sourceid = signaljourneyaudienceconstraints.sourceid
JOIN signaljourneyconstrainttype sjct ON sjct.constrainttypeid = signaljourneyaudienceconstraints.constrainttypeid

I have read some docs, I think I am on the right lines but I keep getting errors like

sqlalchemy.exc.ArgumentError: Join target SignalJourneyAudiences.segment does not refer to a mapped entity

Which I get because SignalJourneyAudiences.segment is not a key, I was trying to replicate the SQL query which I know works.

@app.get("/get-main-query-data", status_code=status.HTTP_200_OK)
def get_main_query_data():
    """Returns data for the main query."""
    return (
        db.query(
            models.SignalJourneyAudienceConstraints.constraintId,
            models.SignalJourneyAudiences.segment,
            models.SingalJourneySources.source,
            models.SignalJourneyConstraintType.constraintType,
            models.SignalJourneyAudienceConstraints.constraintValue,
            models.SignalJourneyAudienceConstraints.targeting,
            models.SignalJourneyAudienceConstraints.frequency,
            models.SignalJourneyAudienceConstraints.period,
        )
        .join(
            models.SignalJourneyAudiences.segment,
            models.SignalJourneyAudiences.audienceId
            == models.SignalJourneyAudienceConstraints.audienceId,
        )
        .join(
            models.SingalJourneySources.source,
            models.SingalJourneySources.sourceId
            == models.SignalJourneyAudienceConstraints.sourceId,
        )
        .join(
            models.SignalJourneyConstraintType.constraintType,
            models.SignalJourneyConstraintType.constraintTypeId
            == models.SignalJourneyAudienceConstraints.constraintTypeId,
        )
        .all()
    )

Am I right in thinking the db.query() is my select claus and then I do things like joins, filters etc?

any help would be greatly appreciated

Answer 1

I have resolved the issue, i knew I was on the right track.

I was using

.join(
            models.SignalJourneyAudiences.segment,
            models.SignalJourneyAudiences.audienceId
            == models.SignalJourneyAudienceConstraints.audienceId,
        )

instead of

.join(
            models.SignalJourneyAudiences,
            models.SignalJourneyAudiences.audienceId
            == models.SignalJourneyAudienceConstraints.audienceId,
        )

@app.get("/get-main-query-data", status_code=status.HTTP_200_OK)
def get_main_query_data():
    """Returns data for the main query."""
    return (
        db.query(
            models.SignalJourneyAudienceConstraints.constraintId,
            models.SignalJourneyAudiences.segment,
            models.SingalJourneySources.source,
            models.SignalJourneyConstraintType.constraintType,
            models.SignalJourneyAudienceConstraints.constraintValue,
            models.SignalJourneyAudienceConstraints.targeting,
            models.SignalJourneyAudienceConstraints.frequency,
            models.SignalJourneyAudienceConstraints.period,
        )
        .join(
            models.SignalJourneyAudiences,
            models.SignalJourneyAudiences.audienceId
            == models.SignalJourneyAudienceConstraints.audienceId,
        )
        .join(
            models.SingalJourneySources,
            models.SingalJourneySources.sourceId
            == models.SignalJourneyAudienceConstraints.sourceId,
        )
        .join(
            models.SignalJourneyConstraintType,
            models.SignalJourneyConstraintType.constraintTypeId
            == models.SignalJourneyAudienceConstraints.constraintTypeId,
        )
        .all()
    )