初步完成lab4代码

Assignments/Assignment4/src/view_test.sql

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+DROP VIEW
+IF
+	EXISTS v_TrainRoutes;
+DROP VIEW
+IF
+	EXISTS v_StayTimes;
+DROP VIEW
+IF
+	EXISTS v_TrainStationCounts;
+CREATE VIEW v_TrainRoutes AS SELECT
+ID AS TrainID,
+StationID_start,
+StationID_arrive 
+FROM
+	Trains;
+CREATE VIEW v_StayTimes AS SELECT
+TrainID,
+StationID,
+arrive_time,
+leave_time,
+TIMEDIFF( leave_time, arrive_time ) AS StayDuration 
+FROM
+	Passbys;
+CREATE VIEW v_TrainStationCounts AS SELECT
+TrainID,
+COUNT( StationID ) AS StationCount 
+FROM
+	Passbys 
+GROUP BY
+	TrainID;
+SELECT
+	* 
+FROM
+	v_StayTimes 
+WHERE
+	TrainID = 'G103';
+UPDATE v_StayTimes 
+SET StationID = 3 
+WHERE
+	TrainID = 'G103' 
+	AND arrive_time = '2024-03-28 07:13:00';
+SELECT
+	* 
+FROM
+	v_StayTimes 
+WHERE
+	TrainID = 'G103';
+DELETE 
+FROM
+	v_StayTimes 
+WHERE
+	TrainID = 'G103' 
+	AND arrive_time = '2024-03-28 07:13:00';
+SELECT
+	* 
+FROM
+	v_StayTimes 
+WHERE
+	TrainID = 'G103';