Question

我有这个 sql 查询，它通过交叉引用 EquipmentItemReservations 表来查找 EquipmentItem 的当前状态：

SELECT EI.Id, ER.ReservationType AS Status 
FROM EquipmentItems AS EI 
  INNER JOIN EquipmentItemReservations AS ER ON EI.Id = ER.EquipmentItemId 
WHERE IsApproved = 1 
  AND DateShipped IS NOT NULL 
  AND DateReturned IS NULL

预订表的 ReservationType 为“已分配”或“已分配”，在适用的情况下显示为“状态”。

我想扩展此查询以获取不符合要求的设备项，并为其余项设置“可用”AS 状态。

我的目标是拥有包含状态（“已分配”、“已分配”或“可用”）的完整项目列表

Answer 1

我能够通过这个查询实现这一点（使其成为 SQL 视图）：

CREATE VIEW view_EquipmentItemStates AS 
    SELECT EI.Id, ER.ReservationType AS Status 
    FROM EquipmentItems AS EI LEFT JOIN EquipmentItemReservations AS ER 
    ON EI.Id = ER.EquipmentItemId 
    WHERE IsApproved = 1 AND DateShipped IS NOT NULL AND DateReturned IS NULL 
    UNION SELECT EquipmentItems.Id, 'Available' As Status 
    FROM EquipmentItems WHERE EquipmentItems.Id NOT IN (
        SELECT EI.Id FROM EquipmentItems AS EI LEFT JOIN EquipmentItemReservations AS ER 
        ON EI.Id = ER.EquipmentItemIdWHERE IsApproved = 1 AND DateShipped IS NOT NULL 
        AND DateReturned IS NULL)

嵌套查询：选择不在另一个查询结果中的结果

1 个答案: