查询不存在最小ID，速度比较

SELECT id FROM pp_user_id_auto_increment WHERE NOT EXISTS (SELECT 1 FROM pp_user WHERE pp_user.id=pp_user_id_auto_increment.id) AND `status`=0 LIMIT 0,1;        0.075s
-- SELECT id FROM pp_user_id_auto_increment WHERE id NOT IN (SELECT id FROM pp_user) AND `status`=0 ORDER BY id ASC LIMIT 0,1;                                                        0.2s
-- SELECT MIN(id) FROM pp_user_id_auto_increment WHERE id NOT IN (SELECT id FROM pp_user) AND `status`=0 ORDER BY id ASC LIMIT 0,1;                                                 40s

-- SELECT MIN(id) FROM pp_user_id_auto_increment WHERE NOT EXISTS (SELECT 1 FROM pp_user WHERE pp_user.id=pp_user_id_auto_increment.id);                                        200s