PL/SQL异常处理

来源：互联网发布：淘宝刷流量有什么好处编辑：程序博客网时间：2024/05/06 21:58

Exception概述

Exception是一种PL/SQL标识符，当运行的PL/SQL块出现错误或警告，则会触发异常处理。为了提高程序的健壮性，可以在PL/SQL块中引入异常处理部分，进行捕捉异常，并根据异常出现的情况进行相应的处理。
ORACLE异常分为两种类型：系统异常、自定义异常。其中系统异常又分为：预定义异常和非预定义异常。
预定义异常
ORACLE定义了他们的错误编号和异常名字，常见的预定义异常处理如下

错误号

异常错误信息名称

说明

ORA-0001

Dup_val_on_index

违反了唯一性限制

ORA-0051

Timeout-on-resource

在等待资源时发生超时

ORA-0061

Transaction-backed-out

由于发生死锁事务被撤消

ORA-1001

Invalid-CURSOR

试图使用一个无效的游标

ORA-1012

Not-logged-on

没有连接到ORACLE

ORA-1017

无效的用户名/口令

ORA-1403

No_data_found

SELECT INTO没有找到数据

ORA-1422

Too_many_rows

SELECT INTO 返回多行

ORA-1476

Zero-divide

试图被零除

ORA-1722

Invalid-NUMBER

转换一个数字失败

ORA-6500

Storage-error

内存不够引发的内部错误

ORA-6501

Program-error

内部错误

ORA-6502

Value-error

转换或截断错误

ORA-6504

Rowtype-mismatch

宿主游标变量与 PL/SQL变量有不兼容行类型

ORA-6511

CURSOR-already-OPEN

试图打开一个已处于打开状态的游标

ORA-6530

Access-INTO-null

试图为null 对象的属性赋值

ORA-6531

Collection-is-null

试图将Exists 以外的集合( collection)方法应用于一个null pl/sql 表上或varray上

ORA-6532

Subscript-outside-limit

对嵌套或varray索引得引用超出声明范围以外

ORA-6533

Subscript-beyond-count

对嵌套或varray 索引得引用大于集合中元素的个数.

非预定义异常
ORACLE为它定义了错误编号，但没有定义异常名字。我们使用的时候，先声名一个异常名，通过伪过程PRAGMA EXCEPTION_INIT，将异常名与错误号关联起来。
自定义异常
程序员从业务角度出发，制定的一些规则和限制。
异常处理
PL/SQL中，异常处理按个步骤进行：
定义异常

exception_name EXCEPTION;
抛出异常

RAISE exception_name
捕获及处理异常
EXCEPTION
    WHEN e_name1 [OR e_name2 ... ] THEN
        statements;
    WHEN e_name3 [OR e_name4 ... ] THEN
        statements;
        ......
    WHEN OTHERS THEN
        statements;
END;

预定义异常处理示例
一个整除的异常
SQL> declare
2    v_n1 number := 50;
3    v_n2 number := 0 ;
4    v_n3 number;
5 begin
6    v_n3 := v_n1/v_n2;
7    dbms_output.put_line('v_n3=' || v_n3);
8 exception
9    when zero_divide then
10      dbms_output.put_line('v_n2 can' || '''' || 't be 0');
11* end;

v_n2 can't be 0
PL/SQL procedure successfully completed.

VALUE_ERROR(错误号ORA-06502)

SQL> declare
2    v_ename varchar2(3);
3 begin
4    select ename into v_ename from emp where empno = &eno;
5    dbms_output.put_line(v_ename);
6 exception
7    when value_error then
8      dbms_output.put_line('variable datatype length is small');
9 end;
10 /
Enter value for eno: 7788
old   4:   select ename into v_ename from emp where empno = &eno;
new   4:   select ename into v_ename from emp where empno = 7788;
variable datatype length is small
PL/SQL procedure successfully completed.
TOO_MANY_ROWS(对应Oracle错误号ORA-01422)
SQL>declare
2    v_ename emp.ename%type;
3 begin
4    select ename into v_ename from emp where deptno = &deptno;
5    dbms_output.put_line(v_ename);
6 exception
7    when too_many_rows then
8      dbms_output.put_line('Too many rows are returned');
9 end;
10 /
Enter value for deptno: 30
old   4:   select ename into v_ename from emp where deptno = &deptno;
new   4:   select ename into v_ename from emp where deptno = 30;
Too many rows are returned
PL/SQL procedure successfully completed.
非预定义异常示例

非预定义异常使用的基本过程如下
a.定义一个异常名
b.将异常名与异常编号相关联
c.在异常处理部分捕捉并处理异常

SQL> delete from dept where deptno = 10;
delete from dept where deptno = 10
*
ERROR at line 1:
ORA-02292: integrity constraint (SCOTT.FK_DEPTNO) violated - child record found
SQL> declare
2    e_deptid exception;       --定义异常
3    pragma exception_init(e_deptid,-2292);       --将异常和错误号关联
4 begin
5    delete from dept where deptno = 10;
6 exception
7    when e_deptid then         --捕获异常
8      dbms_output.put_line('There is record at sub table');
9 end;
10 /
There is record at sub table
PL/SQL procedure successfully completed.
自定义异常示例
自定义异常与Oracle错误没有任何关系，由开发人员为特定情况所定义的例外。下面的例子中，通过自定义异常，当雇员编号不存在时，PL/SQL代码能够给出适当的提示
对于自定义的异常处理需要显示的触发，其步骤如下
a.定义异常(在declare部分进行定义)
b.显示触发异常(在执行BEGIN部分触发异常，使用RAISE语句)
c.引用异常(在EXCEPTION部分捕捉并处理异常)
SQL> update emp set deptno=20 where empno=1111;
0 rows updated.
SQL> declare
2    e_integrity exception;
pragma exception_init(e_integrity,-2291);
4    update emp set deptno = &dno where empno = &eno;
e_no_employee exception;
begin
update emp set deptno = &dno where empno = &eno;
if sql%notfound then
    raise e_no_employee;
end if;
10 exception
11    when e_integrity then
    dbms_output.put_line('The dept does not exists');
when e_no_employee then
    dbms_output.put_line('The employess does not exists');
15 end;
16 /
Enter value for dno: 20
Enter value for eno: 1111
old   6:   update emp set deptno = &dno where empno = &eno;
new   6:   update emp set deptno = 20 where empno = 1111;
The employess does not exists
PL/SQL procedure successfully completed.
工资如果少于1500，则抛出异常
SQL> declare
2    v_empno emp.empno%type;
3    v_sal   emp.sal%type;
4    e_sal exception;
5 begin
6    v_empno := &empno;
7    v_sal   := &sal;
8    insert into emp(empno,sal) values(v_empno,v_sal);
9    if v_sal < 1500 then
10      raise e_sal;
11    end if;
12 exception
13    when e_sal then
14      rollback;
15      dbms_output.put_line('Salary must be more then 1500');
16 end;
17 /
Enter value for empno: 8888
old   6:   v_empno := &empno;
new   6:   v_empno := 8888;
Enter value for sal: 1234
old   7:   v_sal   := &sal;
new   7:   v_sal   := 1234;
Salary must be more then 1500
PL/SQL procedure successfully completed.
使用异常函数处理异常

SQLCODE与SQLERRM

SQLCODE与SQLERRM为异常处理函数。函数SQLCODE用于取得Oracle错误号，函数SQLERRM用于取得与错误号对应的相关错误消息
SQL> declare
2    v_ename emp.ename%type;
3 begin
4    select ename into v_ename from emp
5    where sal = &sal;
6    dbms_output.put_line('Employee Name:' || v_ename);
7 exception
8    when no_data_found then
9      dbms_output.put_line('The employee does not exists');
10    when others then
11      dbms_output.put_line('Error No:' || SQLCODE);
12      dbms_output.put_line(SQLERRM);
13 end;
14 /
Enter value for sal: 1250
old   5:   where sal = &sal;
new   5:   where sal = 1250;
Error No:-1422
ORA-01422: exact fetch returns more than requested number of rows
PL/SQL procedure successfully completed.
RAISE_APPLICATION_ERROR
调用DBMS_STANDARD(ORACLE提供的包)包所定义的RAISE_APPLICATION_ERROR过程，可以重新定义异常错误消息，它为应用程序提供了一种与ORACLE交互的方法。该函数用于在PL/SQL中定义错误消息，且只能在数据库端的子程序中使用(存储过程、函数、包、触发器)，不能在匿名块和客户端的子程序中使用
使用方法
RAISE_APPLICATION_ERROR(error_number,message[,{true | false}]);
该函数内的错误代码和内容，都是用用户自定义
error_number：用于定义错误号，且错误号从-20000 到-20999 之间，以避免与ORACLE 的任何错误代码发生冲突。
message：用于指定错误消息，且消息长度不能超过k，超出部分将被截取
可选参数true,false:默认值为false，会替换先前的所有错误。当设置为true，则该错误会被放在先前错误堆栈中。
SQL> create or replace procedure raise_comm
2 (v_no emp.empno%type,v_comm out emp.comm%type)
3 as
4 begin
5    select comm into v_comm from emp where empno = v_no;
6    if v_comm is null then
7      raise_application_error(-20001,'This employee has no comm');
8    end if;
9 exception
10    when no_data_found then
    dbms_output.put_line('The employee does not exists');
12 end;
13 /
Procedure created.
SQL> var g_sal number;
SQL> exec raise_comm(7788,:g_sal);
BEGIN raise_comm(7788,:g_sal); END;
*
ERROR at line 1:
ORA-20001: This employee has no comm
ORA-06512: at "SCOTT.RAISE_COMM", line 7
ORA-06512: at line 1
SQL> exec raise_comm(7499,:g_sal);
PL/SQL procedure successfully completed.
SQL> print g_sal;
     G_SAL
----------
       300
PL/SQL编译警告
PL/SQL警告的分类
SEVERE: 用于检查可能出现的不可预料结果或错误结果,例如参数的别名问题.
PERFORMANCE: 用于检查可能引起性能问题,如在INSERT操作是为NUMBER列提供了VARCHAR2类型数据.
INFORMATIONAL: 用于检查程序中的死代码.
ALL: 用于检查所有警告.
控制PL/SQL警告消息
通过设置初始化参数PLSQL_WARNINGS来启用在编译PL/SQL子程序时发出警告消息，缺省为DISABLE:ALL
设置警告消息时有如下不同的范围
系统级别
会话级别
ALTER PROCEDURE      ---只针对设置的过程有效
将特定的消息号设置为错误,也可以激活或禁止特定消息号
SQL> show parameter plsql%ings;
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
plsql_warnings                       string      DISABLE:ALL
SQL> ALTER SYSTEM SET PLSQL_WARNINGS='ENABLE:ALL' |'DISABLE:ALL'
SQL> ALTER SESSION SET PLSQL_WARNINGS='ENABLE:PERFORMANCE' |'DISABLE:ALL'
SQL> ALTER PROCEDURE usp COMPILE PLSQL_WARNINGS='ENABLE:PERFORMANCE';
SQL> alter session set plsql_warnings='enable:(5001,5002)';
SQL> ALTER SESSION SET PLSQL_WARNINGS='ENABLE:SEVERE','DISABLE:PERFORMANCE','ERROR:06002';
PL/SQL编译告警示例
检测死代码
在下面的代码中，ELSE子句永远不会执行,应该避免出现类似的死代码.从Oracle 10g开始,在编写PL/SQL子程序之前开发人员可以激活警告检查.

SQL> alter session set plsql_warnings='enable:informational';
Session altered.

SQL> show parameter plsql_warnings
NAME                                 TYPE                              VALUE
------------------------------------ --------------------------------- ------------------------------
plsql_warnings                       string                            ENABLE:INFORMATIONAL, DISABLE:
                                                                       PERFORMANCE, DISABLE:SEVERE
SQL> create or replace procedure dead_code
2 as
3 x number := 10;
4 begin
5    if x > 10 then
6      x := 1;
7    else
8      x := 2;      --死代码
9    end if;
10 end ;
11 /
SP2-0804: Procedure created with compilation warnings
检测引起性能问题的代码
SQL> alter session set plsql_warnings='enable:performance';
Session altered.
SQL> create or replace procedure update_sal
2   (no number,salary varchar2)
3   as
4   begin
5     update emp set sal=salary where empno=no;
6   end;
7   /
SP2-0804: Procedure created with compilation warnings
SQL> show errors
Errors for PROCEDURE UPDATE_SAL:
LINE/COL ERROR
-------- ---------------------------------------------------------------------------------------------------
5/23     PLW-07202: bind type would result in conversion away from column type

参考至:http://blog.csdn.net/robinson_0612/article/details/6080119
              http://www.cnblogs.com/soundcode/archive/2012/01/10/2318385.html

http://blog.csdn.net/endless_horizen/article/details/6563034

http://www.stanford.edu/dept/itss/docs/oracle/10g/server.101/b10755/initparams165.htm

本文原创，转载请注明出处、作者

如有错误，欢迎指正

邮箱:czmcj@163.com

原文出处：http://czmmiao.iteye.com/blog/18367

0 0