Question

我对触发函数PF('myDialog').show();感到困惑。

我对这个函数有一个基本的想法，它返回一个Columns_Update()，它用于获取触发器中的更新列

即使我找到了获取更新列名称的代码，但在位表示方面仍然存在混淆。如果有人解释这个功能或提供参考

，我将非常感激

我有以下功能

varbinary

并在触发器中使用该功能

CREATE FUNCTION dbo.GenColUpdated
(@Col INT, @ColTotal INT)
RETURNS INT
AS
BEGIN;


DECLARE
@ColByte INT,
@ColTotalByte INT,
@ColBit INT;
-- Calculate Byte Positions
SET @ColTotalByte = 1 + ((@ColTotal-1) /8);
SET @ColByte = 1 + ((@Col-1)/8);
SET @ColBit = @Col - ((@ColByte-1) * 8);
RETURN Power(2, @ColBit + ((@ColTotalByte-@ColByte) * 8)-1);
END;

我不明白这种情况

set @ColUpdatedTemp = dbo.GenColUpdated(@ColCounter, @ColTotal) ;

If COLUMNS_UPDATED() & dbo.GenColUpdated(@ColCounter, @ColTotal) = @ColUpdatedTemp

对我来说没有任何意义。首先你要分配价值而不是检查它

Answer 1

您可以查看这个微软的例子

IF EXISTS(SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
   WHERE TABLE_NAME = 'employeeData')
   DROP TABLE employeeData;
IF EXISTS(SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
   WHERE TABLE_NAME = 'auditEmployeeData')
   DROP TABLE auditEmployeeData;
GO
CREATE TABLE dbo.employeeData (
   emp_id int NOT NULL PRIMARY KEY,
   emp_bankAccountNumber char (10) NOT NULL,
   emp_salary int NOT NULL,
   emp_SSN char (11) NOT NULL,
   emp_lname nchar (32) NOT NULL,
   emp_fname nchar (32) NOT NULL,
   emp_manager int NOT NULL
   );
GO
CREATE TABLE dbo.auditEmployeeData (
   audit_log_id uniqueidentifier DEFAULT NEWID() PRIMARY KEY,
   audit_log_type char (3) NOT NULL,
   audit_emp_id int NOT NULL,
   audit_emp_bankAccountNumber char (10) NULL,
   audit_emp_salary int NULL,
   audit_emp_SSN char (11) NULL,
   audit_user sysname DEFAULT SUSER_SNAME(),
   audit_changed datetime DEFAULT GETDATE()
   );
GO
CREATE TRIGGER dbo.updEmployeeData 
ON dbo.employeeData 
AFTER UPDATE AS
/*Check whether columns 2, 3 or 4 have been updated. If any or all
 columns 2, 3 or 4 have been changed, create an audit record. The 
bitmask is: power(2,(2-1))+power(2,(3-1))+power(2,(4-1)) = 14. To test 
whether all columns 2, 3, and 4 are updated, use = 14 instead of >0
 (below).*/

   IF (COLUMNS_UPDATED() & 14) > 0
/*Use IF (COLUMNS_UPDATED() & 14) = 14 to see whether all columns 2, 3, 
and 4 are updated.*/
      BEGIN
-- Audit OLD record.
      INSERT INTO dbo.auditEmployeeData
         (audit_log_type,
         audit_emp_id,
         audit_emp_bankAccountNumber,
         audit_emp_salary,
         audit_emp_SSN)
         SELECT 'OLD', 
            del.emp_id,
            del.emp_bankAccountNumber,
            del.emp_salary,
            del.emp_SSN
         FROM deleted del;

-- Audit NEW record.
      INSERT INTO dbo.auditEmployeeData
         (audit_log_type,
         audit_emp_id,
         audit_emp_bankAccountNumber,
         audit_emp_salary,
         audit_emp_SSN)
         SELECT 'NEW',
            ins.emp_id,
            ins.emp_bankAccountNumber,
            ins.emp_salary,
            ins.emp_SSN
         FROM inserted ins;
   END;
GO

/*Inserting a new employee does not cause the UPDATE trigger to fire.*/
INSERT INTO employeeData
   VALUES ( 101, 'USA-987-01', 23000, 'R-M53550M', N'Mendel', N'Roland', 32);
GO

/*Updating the employee record for employee number 101 to change the 
salary to 51000 causes the UPDATE trigger to fire and an audit trail to 
be produced.*/

UPDATE dbo.employeeData
   SET emp_salary = 51000
   WHERE emp_id = 101;
GO
SELECT * FROM auditEmployeeData;
GO

/*Updating the employee record for employee number 101 to change both 
the bank account number and social security number (SSN) causes the 
UPDATE trigger to fire and an audit trail to be produced.*/

UPDATE dbo.employeeData
   SET emp_bankAccountNumber = '133146A0', emp_SSN = 'R-M53550M'
   WHERE emp_id = 101;
GO
SELECT * FROM dbo.auditEmployeeData;

GO

Columns_update（）函数如何在触发器中工作以查找更新的列名称

1 个答案: