Abstract: Embodiments relate to a system, computer program product and method for database query optimization. An aspect includes a method that extracts complex predicates from a query statement, the query statement having at least two complex predicates. The method then executes a query associated with the query statement and obtains at least a respective execution structure cost (?Ti) for each of the complex predicates. The method also calculates an overall execution structure cost corresponding to each of the complex predicates, the complex predicates being arranged according to result of the query and the execution structure costs (?Ti); and optimizes a database query by selecting the arrangement of complex predicates having a lowest overall execution structure cost.

Abstract: The automatic ball collection system contains a blower sub-system and a collection device. The blower sub-system drives the balls on the ground towards the collection device, and the balls are then automatically collected by the collection device. The blower sub-system contains a number of blowing devices configured at the corners capable of producing air flow substantially along ground surface so as to push the balls to roll towards the collection device. As such, the players' time and effort in constant bending and picking up balls, and the possible injury resulted as such are avoided.

Abstract: Controlling a dump for a database by determining a state of a diagnosis flag associated with the structured query language (SQL) statement in response to a SQL statement being executed for the database. The diagnosis flag is used to indicate if a database dump should be performed. A database dump is performed for the SQL statement in response to determining that the diagnosis flag indicates that a dump is to be performed.

Abstract: The invention provides a method for verifying correctness of a database system, comprising: receiving SQL instruction; extending access paths of the received SQL instruction; executing the SQL instruction by using the extended access paths; and verifying correctness of the database system according to result of executing the SQL instruction. With the method and system of the invention, the object of verifying correctness of a database system by automatically extending access paths of SQL statement may be achieved, and the object of verifying correctness of a database system scientifically, effectively and purposefully based on ratio of error or defect present in database itself due to various data manipulation approaches (different values of access path elements) may also be achieved.