SQL WASE IN与CASE

Question

我有这样的where子句

    ... Where TruckID IN (select VanID from Vantbl)

我喜欢用一个案例，这样可以足够聪明

我有以下

     ...  Where TruckID IN 
       CASE WHEN @VehicleType = 'VAN'
        THEN (select VanID from Vantbl)
      CASE WHEN @VehicleType = 'SUV'
       THEN (select SUVID from SUVtbl)
     END

但nto似乎有效。 我可以通过任何方式使其正常工作。

Answer 1

我建议使用EXISTS而不是IN ：

WHERE EXISTS (
    SELECT 1
    FROM Vantbl
    WHERE @VehicleType = 'VAN' AND TruckID = VanID
) OR EXISTS (
    SELECT 1
    FROM SUVtbl
    WHERE @VehicleType = 'SUV' AND TruckID = SUVID 
)

Answer 2

假设Trucks有零个或一个Vantbl / SUBtbl记录，请尝试此操作。

SELECT *
  FROM Trucks t
    LEFT JOIN Vantbl v ON v.VanID = t.TruckID
    LEFT JOIN SUVtbl s ON s.SUVID = t.TruckID
  WHERE (@VehicleType = 'VAN' AND v.VanID IS NOT NULL)
    OR (@VehicleType = 'SUV' AND s.SUVID IS NOT NULL)

Answer 3

我不了解CASE但您是否考虑过使用UNION ALL ？

(
SELECT ...
FROM  ...
INNER JOIN VanTbl ON ...
WHERE @VehicleType = 'VAN'
)
UNION ALL
(
SELECT ...
FROM ...
INNER JOIN SUVtbl ON ...
WHERE @VecicleType = 'SUV'
);

Answer 4

在基本的布尔逻辑可以做到的情况下，无需CASE：

...
WHERE
    (@VehicleType = 'VAN' AND TruckID IN (SELECT VanID FROM Vantbl))
    OR (@VehicleType = 'SUV' AND TruckID IN (SELECT SUVID FROM SUVtbl))

（假设Vantbl.VanID和SUVtbl.SUVID不能为NULL。）