Вес баз данных

SELECT table_schema AS "Database", 
ROUND(SUM(data_length + index_length) / 1024 / 1024 / 1024, 2) AS "Size (GB)" 
FROM information_schema.TABLES 
GROUP BY table_schema;

Размер таблиц, включая отдельно данные и отдельно индексы.

SELECT CONCAT(table_schema, '.', table_name),
       CONCAT(ROUND(table_rows / 1000000, 2), 'M')                                    `rows`,
       CONCAT(ROUND(data_length / ( 1024 * 1024 * 1024 ), 2), 'G')                    DATA,
       CONCAT(ROUND(index_length / ( 1024 * 1024 * 1024 ), 2), 'G')                   idx,
       CONCAT(ROUND(( data_length + index_length ) / ( 1024 * 1024 * 1024 ), 2), 'G') total_size,
       ROUND(index_length / data_length, 2)                                           idxfrac
FROM   information_schema.TABLES
ORDER  BY data_length + index_length DESC
LIMIT  20;