19. A computer system for retrieving data from a plurality of data sources, said computer system comprising: a first computer device; a query database in communication with the first computer device, the query database configured to store a plurality of query definitions, wherein a first query definition of the plurality of query definitions comprises a first query block including a reference to a first data source and a second query block including a reference to a second data source; a query service executed by the first computer device, the query service configured to instruct the first computer device to: create a first executable query based at least in part on the first query block and a second executable query based at least in part on the second query block; determine an amount of data each of the first executable query and the second executable query are known to access; assign a priority level to each of the first executable query and the second executable query based on the determined amount of data each of the first executable query and the second executable query are known to access; concurrently execute the first executable query at the first data source to create first query results and the second executable query at the second data source to create second query results based on the assigned priority level of the first executable query and the second executable query; and a query results database configured to store the first query results and the second query results.
20. The system of claim 19 , further comprising a query developer user interface configured to receive the first query definition from a user, and transmit the first query definition to the first computer device.