8. A system for database query, comprising: obtaining means configured to obtain, in response to a query request, a first query plan for minimum query response time and a second query plan for minimum query total time for the query request, executing means configured to execute the first query plan and the second query plan at substantially a same time; controlling means configured to detect whether execution of the second query plan reaches a specified point; and outputting means configured to output query results; wherein before the controlling means detects that the execution of the second query plan reaches the specified point, the outputting means outputs an initial query result obtained from the execution of the first query plan, and wherein in response to the controlling means detecting that the execution of the second query plan reaches the specified point, the executing means continues the execution of the second query plan to cause the outputting means to output remaining query results, wherein the first query plan is a query plan using a nested loop join operation, the second query plan is a query plan using a sort merge join operation and the specified point is a point where a construction stage of the sort merge join operation ends, wherein in the construction stage of the sort merge join operation, another table which is not a driving table of the first query plan is sorted according to a join column to obtain a sorted table of the another table, and wherein the executing means continuing the execution of the second query plan comprises: the executing means performing no operation of an execution stage of the second query plan using the sort merge join on records already subjected to the nested loop join operation of the first query plan in the driving table of the first query plan.
19. The system according to claim 8 , wherein the query request is made for at least one of: a plurality of tables; a plurality of intermediate query result sets; and a table and an intermediate query result set in the database.