Biggest Tables across MySQL Server, taken from http://www.mysqlperformanceblog.com/2008/02/04/finding-out-largest-tables-on-mysql-server/

biggest.sql

SELECT CONCAT(table_schema, '.', table_name),
       ROUND(table_rows / 1000000, 2)                                    rowsInMega,
       ROUND(data_length / ( 1024 * 1024 * 1024 ), 2)                    dataInGiga,
       ROUND(index_length / ( 1024 * 1024 * 1024 ), 2)                   idxInGiga,
       ROUND(( data_length + index_length ) / ( 1024 * 1024 * 1024 ), 2) totalSizeInGiga,
       ROUND(index_length / data_length, 2)                                           idxfrac
FROM   information_schema.TABLES
ORDER  BY data_length + index_length DESC
LIMIT  30;