CREATE TABLE table_19412902_1 (group_stage VARCHAR2, play_off VARCHAR2, clubs VARCHAR2)

which group stage was there 0 play-offs and 12 clubs played in it
SELECT COUNT(group_stage) FROM table_19412902_1 WHERE play_off = 0 AND clubs = 12
SELECT COUNT("group_stage") FROM "table_19412902_1" WHERE "clubs" = 12 AND "play_off" = 0