我一直在想这个问题。
提供数据库包含以下列：customer\u id、date、trigger、priority、priorityoverride。
我有一个在priority和priorityoverride之间选择最大值的查询，但我似乎无法同时选择取值的行。
以下是我目前的疑问：

SELECT
Customer_ID,
CASE WHEN offers.PriorityOverride > 0 THEN offers.PriorityOverride ELSE 
Priority END AS 'Priority'
FROM
(
SELECT
    Customer_ID,
    MAX(Priority) AS Priority,
    MAX(PriorityOverride) AS PriorityOverride
FROM
    offers
GROUP BY
    CUstomer_ID
) AS offers

上面的查询选择priority和priorityoverride的最大值，并选择较大的值。
现在，我在选择优先权的日期和触发列时遇到了麻烦。
编辑：更多信息：priorityoverride可以为null或空，但如果它不为空或null，则其值将取代任何优先级。
edit2:这是我更新的查询：

SELECT Customer_ID, Date, Trigger_1, Priority, PriorityOverride
  FROM Offers
  WHERE (Customer_ID, Priority) in (
    SELECT
        Customer_ID,
        CASE WHEN
            MAX(PriorityOverride) > 0
        THEN
            MAX(PriorityOverride)
        ELSE
            MAX(Priority)
        END AS 'Priority'
    FROM
        Offers
    GROUP BY
        Customer_ID
  ) 
  OR (Customer_ID, PriorityOverride) in (
    SELECT
        Customer_ID,
        CASE WHEN
            MAX(PriorityOverride) > 0
        THEN
            MAX(PriorityOverride)
        ELSE
            MAX(Priority)
        END AS 'Priority'
    FROM
        Offers
    GROUP BY
        Customer_ID
  )

但是，上面的查询给了我一个错误“errors:a expression of non-boolean type specified in a context where a condition is expected，near'，'”