# single database
SELECT  SUM(((DATA_LENGTH + INDEX_LENGTH)/1024/1024)) AS "MB"
        FROM INFORMATION_SCHEMA.TABLES
	WHERE TABLE_SCHEMA = "wordpress";


# all instance
SELECT TABLE_SCHEMA as 'Database',
       SUM(((DATA_LENGTH + INDEX_LENGTH)/1024/1024)) AS "MB"
       FROM INFORMATION_SCHEMA.TABLES
       GROUP BY table_schema