Question

我有2个桌子House和AlarmInstall ... 我需要创建一个触发器，以便在我的警报安装表中插入uninstallDate（相异然后为Null）时，在房屋表中将布尔属性“ isInstaled”更新为false。在SQL Server中触发时，我有点菜鸟。任何帮助将不胜感激！！！

这是2张桌子

            [dbo].[AlarmInstall](
                [AlarmInstallId] [int] IDENTITY(1,1) NOT NULL,
                [HouseId] [int] NOT NULL,
                [InstallDate] [date] NOT NULL,
                [uninstallDate] [date] NOT NULL,
                [Model] [nchar](10) NOT NULL,


            [dbo].[House](
                [HouseId] [int] IDENTITY(1,1) NOT NULL,
                [StreetId] [int] NOT NULL,
                [DoorNr] [nchar](10) NOT NULL,
                [CityId] [int] NOT NULL,
                [IsInstalled] [bit] NULL,

两个表都通过HouseId关联，HouseId在House Table中为PK，而在AlarmInstall中为FK

尝试使用此触发器，但我的所有房屋均被标记为真！！！开始

            CREATE TRIGGER STATECHANGE
               ON  dbo.AlarmInstall
            AFTER INSERT, UPDATE
            AS 
            BEGIN
                -- SET NOCOUNT ON added to prevent extra result sets from
                -- interfering with SELECT statements.
                SET NOCOUNT ON;

            update dbo.House SET IsInstalled=1
            From  dbo.AlarmInstall a
            inner join inserted i on a.HouseId=i.HouseId
            and i.InstallDate is not null
            END

Answer 1

我认为这可以帮助：https://www.mssqltips.com/sqlservertip/4024/sql-server-trigger-after-update-for-a-specific-value/

您还可以使用带有以下定义的isInstalled计算字段：

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但是我看不到像这样创建它（或使用触发器）的价值，因为当您没有此字段时，您总是可以在查询中计算它：

CREATE TABLE House(
   HouseId int NOT NULL,
   [...]
   uninstallDate date NULL,
   isInstalled bit AS CASE WHEN uninstallDate IS NULL THEN 0 ELSE 1 END

//已添加到原始答案

SELECT
   HouseId,
   [...]
   uninstallDate,
   CASE WHEN uninstallDate IS NULL THEN 0 ELSE 1 END AS isInstalled
FROM
   House

如果一个表中的值从Null更改为另一值，则触发

1 个答案: