MySQL - LEFT JOIN with GROUP_CONCAT with 3 tables - unknown column

Question

I'm trying to join 3 tables and do a GROUP_CONCAT, but get

Unknown column 'program_outcome.program_outcome_pk' in 'field list'

Query:

SELECT program_outcome.program_outcome_pk, 
       program_outcome.program_outcome, 
       GROUP_CONCAT(program_outcome_unit_outcome_lookup.unit_outcome_pk) unit_outcome_pks, 
       GROUP_CONCAT(unit_outcome.unit_outcome) unit_outcomes 
FROM   program_outcome po 
       LEFT JOIN program_outcome_unit_outcome_lookup pouo 
               ON po.program_outcome_pk = pouo.program_outcome_fk
       LEFT JOIN unit_outcome uo 
               ON pouo.unit_outcome_fk = uo.unit_outcome_pk 
GROUP  BY po.program_outcome_pk, 
          po.program_outcome

The results that I'm looking for are like:

+----------------------------------+--------------------------------------------------+
| program_outcome.program_outcome  |  unit_outcome.unit_outcome                       |
+----------------------------------+--------------------------------------------------+
| program outcome 1                | unit_outcome 2, unit_outcome 5                   |
| program outcome 2                | unit_outcome 7, unit_outcome 1                   |
| program outcome 3                | unit_outcome 1, unit_outcome 9, unit_outcome 11  |
+----------------------------------+--------------------------------------------------+

db fiddle

Answer 1

You need to use the aliases you defined in your from and join claues:

SELECT po.program_outcome_pk, 
       po.program_outcome, 
       GROUP_CONCAT(pouo.unit_outcome_fk) unit_outcome_pks, 
       GROUP_CONCAT(uo.unit_outcome) unit_outcomes 
FROM   program_outcome po 
       LEFT JOIN program_outcome_unit_outcome_lookup pouo 
               ON po.program_outcome_pk = pouo.program_outcome_fk
       LEFT JOIN unit_outcome uo 
               ON pouo.unit_outcome_fk = uo.unit_outcome_pk 
GROUP  BY po.program_outcome_pk, 
          po.program_outcome

Answer 2

You can remove the aliases since your tables doesn't have conflicting names, here is a working Query based on your fiddle:

SELECT program_outcome_pk, 
       program_outcome, 
       GROUP_CONCAT(unit_outcome_pk) unit_outcome_pks, 
       GROUP_CONCAT(unit_outcome) unit_outcomes 
FROM   program_outcome po 
       LEFT JOIN program_outcome_unit_outcome_lookup pouo 
               ON po.program_outcome_pk = pouo.program_outcome_fk
       LEFT JOIN unit_outcome uo 
               ON pouo.unit_outcome_fk = uo.unit_outcome_pk 
GROUP  BY po.program_outcome_pk, 
          po.program_outcome