sql-server - 根据更新后触发器插入更改日志

Question

我需要编写一个 AFTER UPDATE 触发器。当员工表的工资率被修改时。它需要获取该信息并在 ChangeLog 表中创建一行。我的表格如下:

员工:

EmployeeID INT (PK),
PayPerHour MONEY

变更日志:

ChangeID INT (PK),
EmpID (FK to EmployeeID),
ChangedBy NVARCHAR(30),
DateChanged SMALLDATETIME,
OldRate MONEY,
NewRate MONEY

这是我整理的内容。没有错误，但它没有在变更日志中创建行。 (我的印象是插入=新数据，删除=旧数据)。理想情况下，EmpID 将匹配，ChangedBy 将是系统用户，DateChanged 将是时间戳，OldRate 将是更新前的速率，NewRate 将是更新后的速率。

CREATE TRIGGER PayRate_UPDATE
ON Employees
AFTER UPDATE
AS
BEGIN
DECLARE @EmpID INT
SELECT @EmpID = EmployeeID
FROM inserted

DECLARE @OldRate MONEY
SELECT @OldRate = PayPerHour
FROM deleted

DECLARE @DateChanged SMALLDATETIME
SELECT @DateChanged = GETDATE()

DECLARE @ChangedBy NVARCHAR(128)
SELECT @ChangedBy = suser_sname()

DECLARE @NewRate MONEY
SELECT @NewRate = PayPerHour
FROM inserted

IF UPDATE(PayPerHour)
    UPDATE ChangeLog
        SET EmpID = @EmpID,
            ChangedBy = @ChangedBy,
            DateChanged = @DateChanged,
            OldRate = @OldRate,
            NewRate = @NewRate
END;

Answer 1

您的代码中存在一些问题:

1. 触发器必须处理一组更新(而不是单个更新)
2. 您的触发器对您的变更日志进行更新而不是插入

您的代码应该看起来更像:

CREATE TRIGGER PayRate_UPDATE ON Employees
AFTER UPDATE
AS
 BEGIN

    DECLARE @DateChanged SMALLDATETIME
    SELECT  @DateChanged = GETDATE()

    DECLARE @ChangedBy NVARCHAR(128)
    SELECT  @ChangedBy = SUSER_SNAME()

  IF UPDATE(PayPerHour) 
  INSERT  [ChangeLog]
          (
            EmpID,
            ChangedBy,
            DateChanged,
            OldRate,
            NewRate
          )
          SELECT
            i.EmployeeID,
            @ChangedBy,
            @DateChanged,
            d.PayPerHour,
            i.PayPerHour
          FROM
            INSERTED i
            LEFT JOIN DELETED d
              ON i.EmployeeID = d.EmployeeID

  END;

所以，修改后的触发器现在可以处理每个人都加薪的情况，例如

UPDATE Employees SET PayPerHour = PayPerHour  * 1.1 -- everyone gets a 10% payrise YAY!

您的变更日志确实保留了每个员工工资率的每次更新的历史记录。