LISTAGG Query “ORA-00937: not a single-group group function” [duplicate]

Answer 1

I think for your query to work, you need to add a group by, change the order by. You should also use proper explicit join syntax:

SELECT r.rule_id as RULE_ID, 
       LISTAGG(a.ATTRIBUTE_ID, ', ') WITHIN GROUP (ORDER BY a.ATTRIBUTE_ID) as "ATTR_IDS"
FROM N_RULE r JOIN
     N_ATTRIBUTE a 
     ON r.RULE_ID = a.RULE_ID 
GROUP BY r.rule_id
ORDER BY r.rule_id;

Or, possibly you want to include other attribute in the results:

SELECT r.rule_id, r.AUDIENCE, UPPER(r.NAME) 
       LISTAGG(a.ATTRIBUTE_ID, ', ') WITHIN GROUP (ORDER BY a.ATTRIBUTE_ID) as "ATTR_IDS"
FROM N_RULE r JOIN
     N_ATTRIBUTE a 
     ON r.RULE_ID = a.RULE_ID 
GROUP BY r.rule_id, r.AUDIENCE, UPPER(r.NAME)
ORDER BY r.AUDIENCE, UPPER(r.NAME);