Left join unknown column

Question

I am getting Unknown column 'assessment_assessment_type_lookup.assessment_type_fk' in 'on clause' with the query below. The tables and columns are correct.

SELECT * FROM assessment
LEFT JOIN assessment_type 
ON assessment_type.assessment_type_pk = assessment_assessment_type_lookup.assessment_type_fk
LEFT JOIN assessment as ass
ON ass.assessment_pk = assessment_assessment_type_lookup.assessment_fk
LEFT JOIN unit_outcome
ON unit_outcome.unit_outcome_pk = unit_unit_outcome_lookup.unit_outcome_fk
LEFT JOIN unit
ON unit.unit_pk = unit_unit_outcome_lookup.unit_fk
LEFT JOIN unit_outcome as uo
ON uo.unit_outcome_pk = unit_outcome_assessment_lookup.unit_outcome_fk
LEFT JOIN assessment as ass2
ON ass2.assessment_pk = unit_outcome_assessment_lookup.assessment_fk
AND unit.unit_pk = '$unit_pk' GROUP BY assessment.assessment_pk

Answer 1

You are trying to join assessment and assessment_type via table assessment_assessment_type_lookup which can not be done.

If you wish to join 2 tables, you must use both of them in their ON clause.