Bases

SELECT table_schema AS "MaBase",
 ROUND(SUM(data_length + index_length) / 1024 / 1024, 2) AS "Taille en (MB)"
 FROM information_schema.TABLES
 GROUP BY table_schema;

Tables

SELECT table_name AS  "MaBase",
 ROUND(((data_length + index_length) / 1024 / 1024), 2) AS "Taille en (MB)"
 FROM information_schema.TABLES
 WHERE table_schema = "NOMDEBASE"
 ORDER BY (data_length + index_length) DESC;