RE:Duda sobre COLUMNS_UPDATED
Copiado del BOL
E. Utilizar COLUMNS_UPDATED
En este ejemplo se crean dos tablas: una tabla employeeData y una tabla auditEmployeeData. La tabla employeeData, que contiene información confidencial de los sueldos de los empleados, puede ser modificada por los miembros del departamento de recursos humanos. Si se cambia el número de seguridad social del empleado, el sueldo anual o el número de cuenta bancaria, se genera un registro de auditoría y se inserta en la tabla de auditoría auditEmployeeData.
Con la función COLUMNS_UPDATED(), es posible comprobar rápidamente cualquier cambio en estas columnas que contienen información confidencial de los empleados. COLUMNS_UPDATED() sólo se puede utilizar de esta manera para intentar detectar modificaciones en las primeras 8 columnas de la tabla.
USE pubs
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 employeeData (
emp_id int NOT NULL,
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 auditEmployeeData (
audit_log_id uniqueidentifier DEFAULT NEWID(),
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 updEmployeeData
ON employeeData
FOR update AS
/*Check whether columns 2, 3 or 4 has been updated. If any or all of 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 check if all columns 2, 3, and 4 are updated, use = 14 in place of >0 (below).*/
IF (COLUMNS_UPDATED() & 14) > 0
/*Use IF (COLUMNS_UPDATED() & 14) = 14 to see if all of columns 2, 3, and 4 are updated.*/
BEGIN
-- Audit OLD record.
INSERT INTO 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 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 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 employeeData
SET emp_bankAccountNumber = '133146A0', emp_SSN = 'R-M53550M'
WHERE emp_id = 101
GO
SELECT * FROM auditEmployeeData
GO