Parece (por esta comunidade e porque não consegui encontrar nenhum exemplo de procedimentos armazenados usando conjuntos de resultados de outros procedimentos armazenados como tabelas em novas tabelas de seleção) que o mysql não suporta isso ou que é ridiculamente difícil fazer o que eu esperava fazer.
Então, em vez de chamar procedimentos armazenados, copiei as consultas para este procedimento final.
DELIMITER $$ CREATE DEFINER=`root`@`localhost` PROCEDURE `get_team_stats_change`( IN team_id INT ) BEGIN SELECT SUM(start_weight) AS start_weight, SUM(start_body_fat) AS start_body_fat, SUM(current_weight) AS current_weight, SUM(current_body_fat) AS current_body_fat, SUM(weight_change) AS weight_change, SUM(body_fat_change) AS body_fat_change FROM ( SELECT ls.person_id, fs.weight AS start_weight, fs.body_fat AS start_body_fat, ls.weight AS current_weight, ls.body_fat AS current_body_fat, fs.weight - ls.weight AS weight_change, fs.body_fat - ls.body_fat AS body_fat_change FROM (SELECT ttd.person_id, bs.weight, bs.body_fat, bs.test_date FROM body_stats AS bs JOIN ((SELECT pbs.person_id, min(bs.test_date) AS first_test, max(bs.test_date) AS last_test FROM body_stats AS bs, person_body_stats AS pbs, team_member AS tm, team AS t WHERE t.team_id = team_id AND tm.team_id = t.team_id AND tm.person_id = pbs.person_id AND pbs.body_stats_id = bs.body_stats_id AND tm.start_date bs.test_date AND bs.test_date >= t.starting_date GROUP BY person_id) AS ttd, person_body_stats AS pbs) ON bs.test_date = ttd.first_test AND pbs.person_id = ttd.person_id AND pbs.body_stats_id = bs.body_stats_id) AS fs, (SELECT ttd.person_id, bs.weight, bs.body_fat, bs.test_date FROM body_stats AS bs JOIN ((SELECT pbs.person_id, min(bs.test_date) AS first_test, max(bs.test_date) AS last_test FROM body_stats AS bs, person_body_stats AS pbs, team_member AS tm, team AS t WHERE t.team_id = team_id AND tm.team_id = t.team_id AND tm.person_id = pbs.person_id AND pbs.body_stats_id = bs.body_stats_id AND tm.start_date bs.test_date AND bs.test_date >= t.starting_date GROUP BY person_id) AS ttd, person_body_stats AS pbs) ON bs.test_date = ttd.last_test AND pbs.person_id = ttd.person_id AND pbs.body_stats_id = bs.body_stats_id) AS ls WHERE ls.person_id = fs.person_id ) AS delta; END