[DB] DB索引值

1. 叢集索引：create clustered index CX_tExaExamClassRoom_ExamRangeID on tExaExamClassRoom(ExamRangeID);
2. 非叢集索引：CREATE NONCLUSTERED INDEX IX_tExaExamSemesterCourse_ExamDateID ON tExaExamSemesterCourse (ExamDateID);