Oracle 12种触发器利用大小应对复杂事务（oracle12种触发器）

Oracle 12种触发器：利用大小应对复杂事务

Oracle 数据库是许多企业和机构的首选数据库管理系统。在 Oracle 中，触发器是一种重要的工具，它们可以让开发人员在数据库中执行自动化操作。这些操作在特定事件发生时被触发，如插入、更新或删除记录。Oracle 提供了 12 种不同类型的触发器，开发人员可以根据需要选择适当的触发器类型以处理复杂事务。

1. BEFORE INSERT 触发器：在插入新行之前触发

BEFORE INSERT 触发器在插入新行之前触发，可以使用该触发器来验证数据是否符合特定要求。

示例代码：

“`sql

CREATE TRIGGER trg_employee_before_insert

BEFORE INSERT ON employee

FOR EACH ROW

BEGIN

IF :NEW.salary

RSE_APPLICATION_ERROR(-20001, ‘Salary must be greater than 3000.’);

END IF;

END;

2. AFTER INSERT 触发器：在插入新行之后触发
AFTER INSERT 触发器在插入新行之后触发，可以使用该触发器来记录已插入行的信息或执行其他相关操作。
示例代码：

```sql
CREATE TRIGGER trg_employee_after_insert
AFTER INSERT ON employee
FOR EACH ROW
BEGIN
    INSERT INTO employee_audit (emp_id, action) VALUES (:NEW.emp_id, 'New employee added.');
END;

3. BEFORE UPDATE 触发器：在更新行之前触发

BEFORE UPDATE 触发器在更新行之前触发，可以使用该触发器来验证数据是否符合特定要求。

示例代码：

“`sql

CREATE TRIGGER trg_employee_before_update

BEFORE UPDATE ON employee

FOR EACH ROW

BEGIN

IF :NEW.salary

RSE_APPLICATION_ERROR(-20001, ‘Salary must be greater than 3000.’);

END IF;

END;

4. AFTER UPDATE 触发器：在更新行之后触发
AFTER UPDATE 触发器在更新行之后触发，可以使用该触发器来记录已更新行的信息或执行其他相关操作。
示例代码：

```sql
CREATE TRIGGER trg_employee_after_update
AFTER UPDATE ON employee
FOR EACH ROW
BEGIN
    INSERT INTO employee_audit (emp_id, action) VALUES (:NEW.emp_id, 'Employee information updated.');
END;

5. BEFORE DELETE 触发器：在删除行之前触发

BEFORE DELETE 触发器在删除行之前触发，可以使用该触发器来验证要删除的数据是否符合特定要求。

示例代码：

“`sql

CREATE TRIGGER trg_employee_before_delete

BEFORE DELETE ON employee

FOR EACH ROW

BEGIN

IF :OLD.emp_id = 1 THEN

RSE_APPLICATION_ERROR(-20001, ‘Cannot delete employee with ID 1.’);

END IF;

END;

6. AFTER DELETE 触发器：在删除行之后触发
AFTER DELETE 触发器在删除行之后触发，可以使用该触发器来记录已删除行的信息或执行其他相关操作。
示例代码：

```sql
CREATE TRIGGER trg_employee_after_delete
AFTER DELETE ON employee
FOR EACH ROW
BEGIN
    INSERT INTO employee_audit (emp_id, action) VALUES (:OLD.emp_id, 'Employee deleted.');
END;

7. BEFORE INSERT OR UPDATE 触发器：在插入或更新行之前触发

BEFORE INSERT OR UPDATE 触发器在插入或更新行之前触发，可以使用该触发器来验证数据是否符合特定要求。

示例代码：

“`sql

CREATE TRIGGER trg_employee_before_insert_or_update

BEFORE INSERT OR UPDATE ON employee

FOR EACH ROW

BEGIN

IF :NEW.salary

RSE_APPLICATION_ERROR(-20001, ‘Salary must be greater than 3000.’);

END IF;

END;

8. AFTER INSERT OR UPDATE 触发器：在插入或更新行之后触发
AFTER INSERT OR UPDATE 触发器在插入或更新行之后触发，可以使用该触发器来记录已插入或更新行的信息或执行其他相关操作。
示例代码：

```sql
CREATE TRIGGER trg_employee_after_insert_or_update
AFTER INSERT OR UPDATE ON employee
FOR EACH ROW
BEGIN
    INSERT INTO employee_audit (emp_id, action) VALUES (:NEW.emp_id, 'Employee information added or updated.');
END;

9. BEFORE DELETE OR UPDATE 触发器：在删除或更新行之前触发

BEFORE DELETE OR UPDATE 触发器在删除或更新行之前触发，可以使用该触发器来验证要删除或更新的数据是否符合特定要求。

示例代码：

“`sql

CREATE TRIGGER trg_employee_before_delete_or_update

BEFORE DELETE OR UPDATE ON employee

FOR EACH ROW

BEGIN

IF :OLD.emp_id = 1 THEN

RSE_APPLICATION_ERROR(-20001, ‘Cannot delete or update employee with ID 1.’);

END IF;

END;

10. AFTER DELETE OR UPDATE 触发器：在删除或更新行之后触发
AFTER DELETE OR UPDATE 触发器在删除或更新行之后触发，可以使用该触发器来记录已删除或更新行的信息或执行其他相关操作。
示例代码：

```sql
CREATE TRIGGER trg_employee_after_delete_or_update
AFTER DELETE OR UPDATE ON employee
FOR EACH ROW
BEGIN
    INSERT INTO employee_audit (emp_id, action) VALUES (:OLD.emp_id, 'Employee deleted or updated.');
END;

11. INSTEAD OF INSERT 触发器：替代插入操作

INSTEAD OF INSERT 触发器可以用于替代插入操作，该触发器在插入新行之前触发。

示例代码：

“`sql

CREATE TRIGGER trg_employee_instead_of_insert

INSTEAD OF INSERT ON employee

FOR EACH ROW

BEGIN

IF :NEW.salary

RSE_APPLICATION_ERROR(-20001, ‘Salary must be greater than 3000.’);

ELSE

INSERT INTO employee (emp_id, first_name, last_name, salary) VALUES (:NEW.emp_id, :NEW.first_name, :NEW.last_name, :NEW.salary);

INSERT INTO employee_audit (emp_id, action) VALUES (:NEW.emp_id, ‘Employee added.’);

END IF;

END;

12. INSTEAD OF DELETE 触发器：替代删除操作
INSTEAD OF DELETE 触发器可以用于替代删除操作，该触发器在删除行之前触发。
示例代码：

```sql
CREATE TRIGGER trg_employee_instead_of_delete
INSTEAD OF DELETE ON employee
FOR EACH ROW
BEGIN
    IF :OLD.emp_id = 1 THEN
        RSE_APPLICATION_ERROR(-20001, 'Cannot delete employee with ID 1.');
    ELSE
        DELETE FROM employee WHERE emp_id = :OLD.emp_id;
        INSERT INTO employee_audit (emp_id, action) VALUES (:OLD.emp_id, 'Employee deleted.');
    END IF;
END;

触发器是 Oracle 数据库中非常重要的工具，可以帮助开发人员处理复杂事务。本文介绍了 Oracle 中的 12 种触发器类型，并提供了相应的示例代码，供开发人员参考和实践。在实际开发中，开发人员可以根据需要选择适当的触发器类型以解决问题并简化事务处理。