存储过程之--MySQL与Oracle实现对比
1. 存储过程简介
我们常用的操作数据库语言SQL语句在执行的时候需要要先编译,然后执行,而存储过程(Stored Procedure)是一组为了完成特定功能的SQL语句集,经编译后存储在数据库中,用户通过指定存储过程的名字并给定参数(如果该存储过程带有参数)来调用执行它。
一个存储过程是一个可编程的函数,它在数据库中创建并保存。它可以有SQL语句和一些特殊的控制结构组成。当希望在不同的应用程序或平台上执行相同的函数,或者封装特定功能时,存储过程是非常有用的。数据库中的存储过程可以看做是对编程中面向对象方法的模拟。它允许控制数据的访问方式。
存储过程通常有以下优点:
(1).存储过程增强了SQL语言的功能和灵活性。存储过程可以用流控制语句编写,有很强的灵活性,可以完成复杂的判断和较复杂的运算。
(2).存储过程允许标准组件是编程。存储过程被创建后,可以在程序中被多次调用,而不必重新编写该存储过程的SQL语句。而且数据库专业人员可以随时对存储过程进行修改,对应用程序源代码毫无影响。
(3).存储过程能实现较快的执行速度。如果某一操作包含大量的Transaction-SQL代码或分别被多次执行,那么存储过程要比批处理的执行速度快很多。因为存储过程是预编译的。在首次运行一个存储过程时查询,优化器对其进行分析优化,并且给出最终被存储在系统表中的执行计划。而批处理的Transaction-SQL语句在每次运行时都要进行编译和优化,速度相对要慢一些。
(4).存储过程能过减少网络流量。针对同一个数据库对象的操作(如查询、修改),如果这一操作所涉及的Transaction-SQL语句被组织程存储过程,那么当在客户计算机上调用该存储过程时,网络中传送的只是该调用语句,从而大大增加了网络流量并降低了网络负载。
(5).存储过程可被作为一种安全机制来充分利用。系统管理员通过执行某一存储过程的权限进行限制,能够实现对相应的数据的访问权限的限制,避免了非授权用户对数据的访问,保证了数据的安全。
二、MySQL存储过程
(1). 格式
MySQL存储过程创建的格式:CREATE PROCEDURE过程名 ([过程参数[,...]])
[特性 ...]过程体
案例分析:
参数
MySQL存储过程的参数用在存储过程的定义,共有三种参数类型,IN,OUT,INOUT,形式如:
CREATE PROCEDURE([[IN |OUT |INOUT ] 参数名数据类形...])
IN 输入参数:表示该参数的值必须在调用存储过程时指定,在存储过程中修改该参数的值不能被返回,为默认值
OUT 输出参数:该值可在存储过程内部被改变,并可返回
INOUT 输入输出参数:调用时指定,并且可被改变和返回
1)不带参数:
mysql>delimiter // mysql> create procedure p1() -> begin -> declare v_ename varchar(10); -> declare v_sal int; -> select ename,sal into v_ename,v_sal from emp where empno=7788; -> select v_ename ; -> select v_sal; -> end; -> // Query OK, 0 rows affected (0.00 sec)mysql> delimiter ;
mysql> call p1();
+---------+ | v_ename | +---------+ | SCOTT | +---------+ 1 row in set (0.00 sec) +-------+ | v_sal | +-------+ | 3000 | +-------+ 1 row in set (0.00 sec) Query OK, 0 rows affected (0.00 sec)
2)in参数:
mysql> delimiter // mysql> create procedure p2(in v_empno int) -> begin -> declare v_ename varchar(10); -> declare v_sal int; -> select ename,sal into v_ename,v_sal from emp where empno=v_empno; -> select v_ename ; -> select v_sal; -> end; -> // Query OK, 0 rows affected (0.00 sec)mysql> delimiter ;
执行:
mysql> call p2(7788);
+---------+ | v_ename | +---------+ | SCOTT | +---------+ 1 row in set (0.00 sec) +-------+ | v_sal | +-------+ | 3000 | +-------+ 1 row in set (0.00 sec) Query OK, 0 rows affected (0.00 sec)
3)out参数:
mysql> delimiter // mysql> create procedure p3(in v_empno int,out v_sal int) -> begin -> declare v_ename varchar(10); -> select ename,sal into v_ename,v_sal from emp where empno=v_empno; -> select v_ename ; -> select v_sal; -> end; -> // Query OK, 0 rows affected (0.00 sec)mysql> delimiter ;
执行:
mysql> call p3(7788,@v_sal); +---------+ | v_ename | +---------+ | SCOTT | +---------+ 1 row in set (0.00 sec) +-------+ | v_sal | +-------+ | 3000 | +-------+ 1 row in set (0.00 sec)
4)存储过程循环
while 循环
mysql> delimiter // mysql> create procedure p_while() begin declare v_empno int; declare v_count int; set v_empno=7788; set v_count=0; while v_count < 10 do insert into emp1 select * from emp where empno=v_empno; set v_count=v_count + 1; end while; end; // mysql> delimiter ;
repeat 循环:
mysql> delimiter // mysql> create procedure p_repeat() begin declare v_empno int; declare v_count int; set v_empno=7788; set v_count=0; repeat insert into emp1 select * from emp where empno=v_empno; set v_count=v_count + 1; until v_count > 10 end repeat; end; // mysql> delimiter ;
loop 循环:
mysql> delimiter // mysql> create procedure p_loop() begin declare v_empno int; declare v_count int; set v_empno=7788; set v_count=0; loop_label:loop insert into emp1 select * from emp where empno=v_empno; set v_count=v_count + 1; if v_count > 10 then leave loop_label; end if; end loop; end; // mysql> delimiter ;
三、Oracle 存储过程
不带参数:
SQL> create or replace procedure proc1 is 3 v_ename emp.ename%type; 4 v_sal emp.sal%type ; 5 6 begin 7 select ename,sal into v_ename,v_sal from emp where empno=&no; 8 dbms_output.put_line(‘Name is : ‘||v_ename||‘ , ‘||‘Salary is : ‘||v_sal); 9 exception 10 when no_data_found then 11 dbms_output.put_line(‘you number is not crrect ,please input again !‘); 12 13 end; 14 / Procedure created
执行:
SQL> exec proc1;
PL/SQL procedure successfully completed
SQL> set serverout on
SQL> /
Name is : SCOTT , Salary is : 3000
PL/SQL procedure successfully completed
带参数的存储过程:
参数定义中,IN、OUT和IN OUT代表参数的三种不同模式:
IN:当调用存储过程时,该模式的形参接收对应实参的值,并且该是只读的,即不能被修改。默认为IN。
OUT:该形参被认为只能写,既只能为其赋值。在存储过程中不能读它的值。返回时,将该形参值传给相应的实参。
IN OUT:都允许
in 参数:
SQL> create or replace procedure proc2 ( v_empno emp.empno%type) is -- 如果不指明参数的模式,默认为in 2 v_ename emp.ename%type; 3 v_sal emp.sal%type; 4 5 begin 6 select ename,sal into v_ename,v_sal from emp where empno=v_empno; 7 dbms_output.put_line(‘Name is : ‘||v_ename||‘ , ‘||‘Salary is : ‘||v_sal); 8 exception 9 when no_data_found then 10 dbms_output.put_line(‘you number is not crrect ,please input again !‘); 11 12 end; 13 / Procedure created
执行:
SQL> exec proc2(7369);
Name is : SMITH , Salary is : 8000
PL/SQL procedure successfully completed
SQL> create or replace procedure proc2 ( v_empno in emp.empno%type) is 2 v_ename emp.ename%type; 3 v_sal emp.sal%type; 4 5 begin 6 select ename,sal into v_ename,v_sal from emp where empno=v_empno; 7 dbms_output.put_line(‘Name is : ‘||v_ename||‘ , ‘||‘Salary is : ‘||v_sal); 8 exception 9 when no_data_found then 10 dbms_output.put_line(‘you number is not crrect ,please input again !‘); 11 12 end; 13 /
out 参数:
SQL> create or replace procedure proc2 ( v_empno in emp.empno%type, v_ename out emp.ename%type,v_sal out emp.sal%type) 2 is 3 4 begin 5 select ename,sal into v_ename,v_sal from emp where empno=v_empno; 6 dbms_output.put_line(‘Name is : ‘||v_ename||‘ , ‘||‘Salary is : ‘||v_sal); 7 exception 8 when no_data_found then 9 dbms_output.put_line(‘you number is not crrect ,please input again !‘); 10 11 end; 12 / Procedure created
执行:
SQL> var v_ename varchar2(10);
SQL> var v_sal number; //注意:对于number类型不能指明长度
SQL> exec proc2(7788,:v_ename,:v_sal );
Name is : SCOTT , Salary is : 3000
PL/SQL procedure successfully completed
v_ename
---------
SCOTT
v_sal
---------
3000
通过匿名块执行:
SQL> var v_ename varchar2 SQL> var v_sal number SQL> declare 2 v_empno emp.empno%type := 7788; 3 begin 4 proc2(v_empno ,:v_ename,:v_sal); 5 end; 6 / Name is : SCOTT , Salary is : 3000 PL/SQL procedure successfully completed v_ename --------- SCOTT v_sal --------- 3000
SQL> declare 2 v_empno emp.empno%type := 7836; 3 v_ename emp.ename%type ; 4 v_sal emp.sal%type; 5 begin 6 proc2(v_empno ,v_ename,v_sal); 7 end; 8 /
in out 参数:
SQL> create or replace procedure proc3( v_empno in out emp.empno%type) is v_ename emp.ename%type; v_sal emp.sal%type; begin select ename,sal into v_ename,v_sal from emp where empno=v_empno; dbms_output.put_line(‘Name is : ‘||v_ename||‘ , ‘||‘Salary is : ‘||v_sal); exception when no_data_found then dbms_output.put_line(‘you number is not crrect ,please input again !‘); end; /
执行:
SQL> var v_empno number;
SQL> exec :v_empno:=7788;
PL/SQL procedure successfully completed
v_empno
---------
7788
SQL> exec proc3(:v_empno);
Employees id is: 7788 , Name is : SCOTT , Salary is : 3000
PL/SQL procedure successfully completed
v_empno
---------
7788
SQL> declare 2 v_empno emp.empno%type; 3 begin 4 v_empno:=7788; 5 proc3(v_empno ); 6 end; 7 / Name is : SCOTT , Salary is : 3000 PL/SQL procedure successfully completed
SQL> create or replace procedure proc3( v_empno in out emp.empno%type) 2 3 is 4 5 v_ename emp.ename%type; 6 v_sal emp.sal%type; 7 8 begin 9 select empno,ename,sal into v_empno, v_ename,v_sal from emp where empno=v_empno; 10 dbms_output.put_line(‘Employee number is: ‘||v_empno||‘ , ‘||‘Name is : ‘||v_ename||‘ , ‘||‘Salary is : ‘||v_sal); 11 exception 12 when no_data_found then 13 dbms_output.put_line(‘you number is not crrect ,please input again !‘); 14 15 end; 16 / Procedure created
执行:
SQL> declare 2 v_empno emp.empno%type; 3 begin 4 v_empno := 7788; 5 proc3(v_empno); 6 end; 7 / Employee number is: 7788 , Name is : SCOTT , Salary is : 3000 PL/SQL procedure successfully completed
Oracle 存储过程循环:
loop 基本循环:
SQL> declare 2 v_empno emp.empno%type := 7788; 3 v_count number :=0; 4 5 begin 6 7 loop 8 insert into emp1 select * from emp where empno=v_empno; 9 v_count := v_count + 1; 10 exit when v_count >= 10; 11 end loop; 12 13 end; 14 / PL/SQL procedure successfully completed
for 循环:
SQL> declare 2 3 v_empno emp.empno%type; 4 5 begin 6 v_empno := 7788; 7 8 for i in 1..10 loop 9 insert into emp1 select * from emp where empno=v_empno; 10 end loop; 11 12 end; 13 14 15 16 / PL/SQL procedure successfully completed
while 循环:
SQL> declare 2 v_empno emp.empno%type; 3 v_count number := 0; 4 5 begin 6 v_empno := 7788; 7 8 while v_count < 10 loop 9 insert into emp1 select * from emp where empno=v_empno; 10 v_count := v_count + 1; 11 12 end loop; 13 end; 14 / PL/SQL procedure successfully completed