A computer system includes: a database server configured to execute a database management system; and a storage apparatus configured to store data. The storage apparatus is configured to have a power saving function for switching between a sleep mode for reducing power consumption of the storage apparatus and an active mode for enabling read and write of the data. The database management system is configured to be executed by the arithmetic device, to thereby: receive a query for reading or writing data; analyze the received query to create an execution plan; identify a volume for reading and writing data; and select an execution plan for which power consumption satisfies a predetermined threshold value based on power consumption information on the identified volume.