什么是正点行车？影响正点行车的因素有哪些？如何保证正点行车？
Which two statements are true about record groups?（） ["They are stored in the database. ","They are stored in local Forms memory. ","The type is specified explicitly at design time. ","The type is implied by when and how it is created."]
Evaluate the following function code： CREATE FUNCTION get_dept_avg（dept_id NUMBER） RETURN NUMBER RESULT_CACHE RELIES_ON （EMPLOYEES） IS avgsal NUMBER（6）； BEGIN SELECT AVG（SALARY）INTO avgsal FROM EMPLOYEES WHERE DEPARTMENT_ID = dept_id； RETURN avgsal； END get_dept_avg； Which statement is true regarding the above function？（） [" The cached result becomes invalid when any structural change is done to the EMPLOYEES table. "," If the function execution results in an unhandled exception，the exception result is also stored in the cache."," Each time the function is invoked in a different session，the current result in the result cache gets overwritten."," If the function is invoked with a different parameter value，the existing result in the result cache gets overwritten by the latest value."]
In Recovery Manager （RMAN）， you have set control file autobackup to ON by using the following command： CONFIGURE CONTROLFILE AUTOBACKUP ON； Which two events would cause the control file to be backed up automatically？ （） [" A tablespace is taken offline."," The database instance is restarted."," A new data file is added to an existing tablespace."," A successful backup is recorded in the RMAN repository."," The RMAN connection is disconnected from the target database."]
司法管辖权的基础是（） ["以地域为基础、以当事人居住地为基础、以合同纠纷中当事人意志为基础","以合同履行地为基础、以当事人国籍为基础、以合同纠纷当事人意志为基础","以合同签订地为基础、以当事人国籍为基础、以合同纠纷当事人意志为基础","以地域为基础、以当事人国籍为基础、以合同纠纷中当事人意志为基础"]
简述往复式压缩机活塞的基本结构型式。
