Oracle对PL/SQL中的异常处理

EXCEPTION
WHEN first_exception THEN <code to handle first exception >
WHEN second_exception THEN <code to handle second exception >
WHEN OTHERS THEN <code to handle others exception >
END;

--例1：更新指定员工工资，如工资小于1500，则加100；
DECLARE
   v_empno employees.employee_id%TYPE := &empno;
   v_sal   employees.salary%TYPE;
BEGIN
   SELECT salary INTO v_sal FROM employees WHERE employee_id = v_empno;
   IF v_sal<=1500 THEN 
        UPDATE employees SET salary = salary + 100 WHERE employee_id=v_empno; 
        DBMS_OUTPUT.PUT_LINE(‘编码为‘||v_empno||‘员工工资已更新!‘);     
   ELSE
        DBMS_OUTPUT.PUT_LINE(‘编码为‘||v_empno||‘员工工资已经超过规定值!‘);
   END IF;
EXCEPTION
   WHEN NO_DATA_FOUND THEN  
      DBMS_OUTPUT.PUT_LINE(‘数据库中没有编码为‘||v_empno||‘的员工‘);
   WHEN TOO_MANY_ROWS THEN
      DBMS_OUTPUT.PUT_LINE(‘程序运行错误!请使用游标‘);
   WHEN OTHERS THEN
      DBMS_OUTPUT.PUT_LINE(SQLCODE||‘—‘||SQLERRM);
END;

<异常情况> EXCEPTION;

PRAGMA EXCEPTION_INIT(<异常情况>, <错误代码>)；

--例2：删除指定部门的记录信息，以确保该部门没有员工。
 
INSERT INTO departments VALUES(50, ‘FINANCE‘, ‘CHICAGO‘);
DECLARE
   v_deptno departments.department_id%TYPE := &deptno;
   deptno_remaining EXCEPTION;--定义一个异常变量
   PRAGMA EXCEPTION_INIT(deptno_remaining, –2292); /* -2292 是违反一致性约束的错误代码 */
BEGIN
   DELETE FROM departments WHERE department_id = v_deptno;
EXCEPTION
   WHEN deptno_remaining THEN 
      DBMS_OUTPUT.PUT_LINE(‘违反数据完整性约束!‘);
   WHEN OTHERS THEN
      DBMS_OUTPUT.PUT_LINE(SQLCODE||‘—‘||SQLERRM);
END;

<异常情况> EXCEPTION;
RAISE <异常情况>；

--例3：更新指定员工工资，增加100；
 
DECLARE
   v_empno employees.employee_id%TYPE :=&empno;
   no_result  EXCEPTION;-定义异常
BEGIN
   UPDATE employees SET salary = salary+100 WHERE employee_id = v_empno;
   IF SQL%NOTFOUND THEN
      RAISE no_result;//触发异常
   END IF;
EXCEPTION
   WHEN no_result THEN //捕捉异常
      DBMS_OUTPUT.PUT_LINE(‘你的数据更新语句失败了!‘);
   WHEN OTHERS THEN
      DBMS_OUTPUT.PUT_LINE(SQLCODE||‘—‘||SQLERRM);

RAISE_APPLICATION_ERROR(error_number,error_message,[keep_errors] );

CREATE OR REPLACE FUNCTION get_salary(p_deptno NUMBER) #函数检索指定部门的工资总和
RETURN NUMBER 
AS
  v_sal NUMBER; #函数get_salary返回v_sal值
BEGIN
  IF p_deptno IS NULL THEN
    RAISE_APPLICATION_ERROR(–20991, '部门代码为空'); #用户定义的异常处理
  ELSIF p_deptno<0 THEN
    RAISE_APPLICATION_ERROR(–20992, '无效的部门代码');
  ELSE
    SELECT SUM(employees.salary) INTO v_sal FROM employees 
    WHERE employees.department_id=p_deptno;
    RETURN v_sal;
  END IF;

DECLARE 
  V_salary NUMBER(7,2);
  V_sqlcode NUMBER;
  V_sqlerr VARCHAR2(512);
  Null_deptno EXCEPTION;  #定义异常情况
  Invalid_deptno EXCEPTION; #定义异常情况
  PRAGMA EXCEPTION_INIT(null_deptno,–20991);  #非预定义的异常，将它与oracle错误联系起来
  PRAGMA EXCEPTION_INIT(invalid_deptno, –20992); #非预定义的异常，将它与oracle错误联系起来
BEGIN
  BEGIN
    V_salary :=get_salary(–10);
  EXCEPTION
    WHEN invalid_deptno THEN
      V_sqlcode :=SQLCODE;
      V_sqlerr  :=SQLERRM;
      INSERT INTO errlog(errcode, errtext) VALUES(v_sqlcode, v_sqlerr); #将错误SQLCODE及SQLERRM存入到表errlog中  
      COMMIT;
  END ;

CREATE OR REPLACE TRIGGER tr_insert_emp
BEFORE INSERT ON employees
FOR EACH ROW
BEGIN
  IF :new.first_name IS NULL OR :new.last_name is null THEN
    RAISE_APPLICATION_ERROR(–20000,‘Employee must have a name.‘);
  END IF;