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Principles_of_Database_System/Assignments/Assignment4/src/view_test.sql
2024-04-07 23:20:02 +08:00

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SQL

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';