Abstract: This specification provides a multi-party database including a central node and a plurality of databases. The central node has a disclosed first interface. Each of a plurality of query engines corresponding to the plurality of databases includes a second interface configured to interact with the first interface. The central node can determine a plurality of target databases related to a query request from the plurality of databases based on the query request; and send a query indication to a plurality of target query engines corresponding to the plurality of target databases through the first interface. The plurality of target query engines can receive the query indication from second interfaces in the plurality of target query engines, and execute the query indication to obtain a query result; and send the query result to the first interface in the central node through the second interfaces.

Abstract: Implementations of this specification provide query optimization methods, apparatuses, and systems for secure multi-party databases. In an implementation, a method includes: receiving a current query associated with a plurality of target database of a multi-party database system, generating a plurality of execution plans for the current query, determining, for each execution plan, a respective cost computation formula of a plurality of cost computation values for computing an execution cost of jointly executing the execution plan by the plurality of target databases, receiving a secure computation result from each of a plurality of query engines corresponding to the plurality of target databases, and determining an optimal execution plan having a lowest cost value in the plurality of cost computation formulas based on the secure computation result.

Abstract: This specification provides example data query methods, apparatuses, and systems for a multi-party secure database. In an example computer-implemented method, a central node receives a data query request from a data requester, where the data query request relates to one or more pieces of target data stored at one or more data providers. The central node determines whether the data query request satisfies respective security requirements of the one or more pieces of target data. In response to determining that the data query request satisfies respective security requirements of the one or more pieces of target data, the central node processes the one or more pieces of target data to obtain result data; and sends the result data to the data requester. The central node can restrict query of the target data by the data requester based on the security requirement of the target data stored at the data provider.