在 SQL Server 中向触发器添加条件

Question

我的 SQL Server 数据库中有这些表：

CREATE TABLE weather 
(
     weatherId integer Identity(1,1) primary key,
     weatherDate datetime,
     rainout BIT,
     temperature float,
     inchesOfRain float
)

CREATE TABLE weather_audit 
(
     weatherAuditId integer Identity(1,1) primary key,
     weatherId integer,
     date datetime,
     rainout BIT,
     temperature float,
     inchesOfRain float
)

CREATE TABLE maintenance 
(
     maintenanceId integer Identity(1,1) primary key,
     maintenanceDescription nvarchar(100),
     dateRequested datetime,
     dateResolved datetime,
     currentStatus nvarchar(20),
     estimatedCost decimal,
)

CREATE TABLE maintenence_audit
(
     mainteneceAuditId integer Identity(1,1) primary key,
     maintenanceId integer,
     description nvarchar(100),
     dateRequested datetime,
     dateResolved datetime,
     currentStatus nvarchar(20),
     estimatedCost decimal,
     updatedOn datetime
)

我想设置一个触发器，当将一行插入到 inchesOfRain 大于 4 的天气表中时触发。这就是我现在所拥有的，但它不起作用：

CREATE TRIGGER tr_weather_ForInsertUpdate 
ON weather
FOR INSERT, UPDATE
AS
BEGIN
    SET NOCOUNT ON

    IF (SELECT TOP 1 inchesOfRain FROM weather) > 4
         INSERT INTO weather_audit (weatherId, weatherDate, rainout, temperature, inchesOfRain)
             SELECT
                 i.weatherId, i.weatherDate, i.rainout, i.temperature, i.inchesOfRain
             FROM 
                 Inserted AS I
END

所以如果我要插入这个

INSERT INTO dbo.weather (weatherDate, rainout, temperature, inchesOfRain)
VALUES ('4/21/2018', '0', '70', '6'); 

它将在weather 表和weather_audit 表中添加一行，因为雨量为 6 英寸

Answer 1

您需要依赖您的 Inserted 伪表来决定是否向审计表中添加一行 - 试试这个：

CREATE TRIGGER tr_weather_ForInsertUpdate 
ON weather
FOR INSERT, UPDATE
AS
BEGIN
    SET NOCOUNT ON

    INSERT INTO weather_audit (weatherId, weatherDate, rainout, temperature, inchesOfRain)
        SELECT
            i.weatherId, i.weatherDate, i.rainout, i.temperature, i.inchesOfRain
        FROM 
            Inserted AS I
        WHERE
            i.inchesOfRain > 4  -- just insert those rows with inchesOfRain > 4
END

Answer 2

你的触发器很好，它只需要是

CREATE TRIGGER tr_weather_ForInsertUpdate 
ON weather
FOR INSERT, UPDATE
AS
BEGIN
    SET NOCOUNT ON

--Modified Code Start
DECLARE @inchesOfRain float
    
SELECT @inchesOfRain = inchesOfRain FROM inserted


    IF @inchesOfRain > 4
    BEGIN
    ---------------Modified COde End
         INSERT INTO weather_audit (weatherId, weatherDate, rainout, temperature, inchesOfRain)
             SELECT
                 i.weatherId, i.weatherDate, i.rainout, i.temperature, i.inchesOfRain
             FROM 
                 Inserted AS I
     END
END

更新：Marc S 代码 sn-p 是完美的答案。