从WHERE子查询SQL Server更新

Question

如何使用UPDATE语句中的子查询？ 这是我的查询：

UPDATE car_availability
SET    availability_status = 'GOOD'
FROM   car_trip AS TRIP
WHERE  car_availability.car_no = TRIP.car_no 
AND NOT EXISTS (SELECT DISTINCT A.car_No 
                FROM   car_maintenance A 
                WHERE  A.car_no = TRIP.vehicle_id 
                AND    start_date = TRIP.workday)
AND EXISTS (SELECT DISTINCT B.car_No 
            FROM   car_maintenance B 
            WHERE  B.car_no = TRIP.vehicle_id 
            AND end_date IS NOT NULL)

我收到错误消息“ UPDATE和DELETE语句中的FROM子句不能包含子查询源或联接。”

我想将Availability_Status更新为GOOD，其中car_maintenance中存在的汽车的start_date等于car_trip的工作日，而car_maintenance中的汽车的结束日期不为空。

Answer 1

正如@McNets所说，您需要将car_availability表添加到FROM子句中。 尝试这个：

UPDATE CA
SET    availability_status = 'GOOD'
FROM   car_availability CA
JOIN car_trip AS TRIP ON CA.car_no = TRIP.car_no 
WHERE NOT EXISTS (SELECT DISTINCT A.car_No 
                FROM   car_maintenance A 
                WHERE  A.car_no = TRIP.vehicle_id 
                AND    start_date = TRIP.workday)
AND EXISTS (SELECT DISTINCT B.car_No 
            FROM   car_maintenance B 
            WHERE  B.car_no = TRIP.vehicle_id 
            AND end_date IS NOT NULL)