SQL Server：根据 ID 更新值而不插入表

Question

ALTER TRIGGER MyTrigger 
ON persons 
AFTER INSERT
AS 
    IF EXISTS(SELECT * 
              FROM Persons t 
              INNER JOIN inserted i ON i.LastName <> t.LastName 
                                    OR i.FirstName <> t.FirstName 
                                    OR i.address <> t.address 
                                    OR i.City <> t.City 
                                    AND i.PersonID = t.PersonID) 
    BEGIN
        UPDATE p 
        SET p.LastName = i.LastName, 
            p.FirstName = i.FirstName,
            p.address = i.address,
            p.City = i.City
        FROM persons AS p
        INNER JOIN inserted i ON p.PersonID <> i.PersonID
        WHERE p.PersonID = i.PersonID 
    END

当我尝试使用以前的 id 插入新列时，该行正在更新，这很好。但是也插入了一个我不想要的新行

Answer 1

我想你正在寻找

CREATE TRIGGER <Trigger Name Here>
ON <Table Name Here>
INSTEAD OF INSERT, UPDATE
AS
  INSERT INTO <Table Name Here>
  SELECT I.*
  FROM INSERTED I INNER JOIN <Table Name Here> T
  ON I.ID <> T.ID; --Insert all rows with the ID does not exists in the table

  UPDATE T
  SET T.FirstName = I.FirstName,
      T.LastName = I.LastName,
      T.Address = I.Address,
      T.City = I.City
  FROM INSERTED I INNER JOIN <Table Name Here> T
  ON T.ID = I.ID --UPDATE all rows with the same ID already exists in the table
  WHERE T.FirstName <> I.FirstName
        AND --OR
        T.LastName <> I.LastName
        AND --OR
        T.Address <> I.Address
        AND --OR
        T.City <> I.City;

• 将 <Trigger Name Here> 替换为触发器的名称。
• 将<Table Name Here> 替换为您的表名。

Answer 2

我认为您应该学习如何使用merge，而不是在触发器中执行此逻辑。但是，您的问题是关于如何使触发器工作。你想要的是一个替换插入的触发器，而不是之后运行。

您需要在触发器内进行插入。这看起来像：

ALTER TRIGGER MyTrigger ON persons INSTEAD OF INSERT
AS 
BEGIN
    -- Insert person ids that are new
    INSERT INTO persons
        SELECT i.*
        FROM inserted i
        WHERE NOT EXISTS (SELECT 1
                          FROM persons p
                          WHERE i.PersonID = p.PersonID
                         );

    -- update existing person ids
    UPDATE p 
        SET p.LastName = i.LastName, 
            p.FirstName = i.FirstName,
            p.address = i.address,
            p.City = i.City
        FROM persons p INNER JOIN
             inserted i
             ON p.PersonID = i.PersonID
        WHERE p.LastName <> i.LastName OR 
              p.FirstName <> i.FirstName OR
              p.address <> i.address OR
              p.City <> i.City;
END;  -- MyTrigger

我保留了您的比较条件，尽管我认为它们不正确。您需要非常小心 NULL 值。如果任何旧值或新值是NULL，则不会出现UPDATE。

Answer 3

为什么不试试这样的存储过程

 create stored procedure USP_UpsertPerson
(
    @personId
    @ other inputsinputs
)


AS 
BEGIN
 IF( @personId IS NOT NULL)
BEGIN
 ----------- here Update table script With @personId
END
ELSE
BEGIN
   ----------- here Insert table script
END
END 
GO

然后当你想要插入时发送@personId为null，当你想要更新时发送id

执行速度比查询快，代码易于引用且运行良好