Din SELECT-forespørgsel mangler en GROUP BY-sætning. Du mener sandsynligvis:
INSERT INTO appfilter2
SELECT userapps.name, GROUP_CONCAT(CONCAT(userapps.activity, '/',userapps.class)) AS activity
FROM userapps
GROUP BY userapps.name
Din SELECT-forespørgsel mangler en GROUP BY-sætning. Du mener sandsynligvis:
INSERT INTO appfilter2
SELECT userapps.name, GROUP_CONCAT(CONCAT(userapps.activity, '/',userapps.class)) AS activity
FROM userapps
GROUP BY userapps.name