Abstract: A big data database system created in a language structure of a SQL database and a language structure of a NoSQL database is provided for accessing data after clients have requested for a connection, and the system includes at least one transfer server and a data host, and the transfer server has a plurality of queuing devices and an assigner, and the queuing devices are telecommunicatively coupled to the clients respectively, and the assigner is telecommunicatively coupled to the queuing devices and the data host. When the clients send out a data request, the respective queuing device receives and queues the data request, and the assigner sends the data request to the data host through a single connection between the transfer server and the data host. Therefore, the connection load of the data host of a terminal is reduced to improve the overall system operation performance.