Oracle笔记：存储过程与函数

01 不带参数存储过程

--创建不带参数(不能加括号表示无参)存储过程
create or replace procedure procedure1
as
--as与is区别：在存储过程（PROCEDURE）和函数(FUNCTION)中没有区别，在视图（VIEW）中只能用AS不能用IS，在游标(CURSOR)中只能用IS不能用AS。
--声明部分
countint number;

--执行部分
begin
select count(1) into countint from emp;
dbms_output.put_line('emp表共有' || countint || '行记录');

--异常处理部分
exception 
    when others
    then
    null;
end;

测试如图：

02 带参数存储过程

--带参数存储过程
--in 参数：用于接收参数，在子程序内部，不能进行修改。默认的参数模式：in
--out 参数：输出模式的参数，用于输出值，会忽略传入的值。在子程序内部可以对其进行修改。调用时参数需要使用变量
--in out 参数：能接收传入的实参值；在子程序内部可以修改,可以输出。调用时参数需要使用变量
--当存储过程中含有输出参数时，调用该存储过程时必须通过begin...end语句块来实现。不能通过exec或call调用

--in 参数
create or replace procedure procedure2(empno_in number)
as
enametmp EMP.ENAME%type;

begin
    select ename into enametmp from emp where empno = empno_in;
    dbms_output.put_line('找到名称' || enametmp);
--    empno_in:=0;--编译不通过
exception 
    when others then 
    dbms_output.put_line('没有找到该名称');
end;


--in out 参数
create or replace procedure procedure3(empno_in in out number)
as
enametmp EMP.ENAME%type;

begin
    select ename into enametmp from emp where empno = empno_in;
    dbms_output.put_line('找到名称' || enametmp);
    empno_in:=0;--调用时参数需要使用变量
exception 
    when others then 
    dbms_output.put_line('没有找到该名称');
end;

--in参数；out 参数
create or replace procedure procedure4(empno_in in number,outename out varchar2,outmsg out varchar2)
as
begin
    select ename into outename from emp where empno = empno_in;
    outmsg:='找到名称' || outename;
exception 
    when others then 
    outmsg:='没有找到该名称';
end;

测试如图：

03 参数默认值存储过程

--带有默认参数存储过程
create or replace procedure procedure5(
no varchar2,
name varchar2,
gentle varchar2 default '男',
age number default 0,
dept varchar2
)
as
begin
insert into stu values(no,name,gentle,age,dept);
commit;
end;

测试如图：

04 函数

CREATE OR REPLACE FUNCTION chk_null (pinput NUMBER)
RETURN CHAR
   IS
   BEGIN
      IF pinput IS NULL
      THEN
         RETURN 'Y';
      ELSE
         RETURN 'N';
      END IF;
   END;

----函数不能重载 ；但是再packages包里是可以的
--CREATE OR REPLACE FUNCTION chk_null (pinput VARCHAR2)
--      RETURN CHAR
--   IS
--   BEGIN
--      IF pinput IS NULL
--      THEN
--         RETURN 'Y';
--      ELSE
--         RETURN 'N';
--      END IF;
--   END;

测试如图：

05 存储过程与函数的区别

1.返回值的区别：函数必须有返回值；而存储过程是通过参数返回的，可以有多个或者没有。存储过程和函数同样支持in，out,in out这三种类型的参数
2.调用的区别：函数可以在查询语句或存储过程中直接调用；而存储过程一般由应用程序调用
3.应用区别：函数一般情况下是用来计算并返回一个计算结果；而存储过程一般是用来完成特定的业务逻辑操作（比如修改、插入数据库表或执行某些DDL语句等等）
4.函数封装功能；存储过程封装业务逻辑

NOTE

create or replace的对象有：functions, procedures, packages, types, synonyms, trigger and views，就是没有table，也没有sequence。drop掉一个并不存在table会报错.
create or replace 表示在创建对象时,如果已存在同名的对象,则重新创建，没有重载的说法，不能试图添加同名不同参数类型或个数的函数或存储过程，只要名称相同都会被覆盖。在packages包中可以重载

ALTER TABLE STU
DROP PRIMARY KEY CASCADE;

DROP TABLE STU CASCADE CONSTRAINTS;
CREATE TABLE STU
(
  NO      VARCHAR2(10 BYTE),
  NAME    VARCHAR2(10 BYTE),
  GENTLE  VARCHAR2(2 BYTE),
  AGE     NUMBER(2),
  DEPT    VARCHAR2(20 BYTE)
);

--------
DROP TABLE EMP CASCADE CONSTRAINT;

CREATE TABLE EMP(
EMPNO NUMBER(4),
ENAME VARCHAR2(10),
JOB VARCHAR2(9),
MGR NUMBER(4),
HIREDATE DATE,
SAL NUMBER(7,2),
COMM NUMBER(7,2),
DEPTNO NUMBER(2)
);

COMMENT ON COLUMN EMP.EMPNO IS '编码';
COMMENT ON COLUMN EMP.ENAME IS '名称';
COMMENT ON COLUMN EMP.JOB IS '工作';
COMMENT ON COLUMN EMP.MGR IS '主管';
COMMENT ON COLUMN EMP.HIREDATE IS '聘用时间';
COMMENT ON COLUMN EMP.SAL IS '工资';
COMMENT ON COLUMN EMP.COMM IS '提成';
COMMENT ON COLUMN EMP.DEPTNO IS '部门编码';

INSERT INTO EMP
SELECT 7369 AS EMPNO, 'SMITH' AS ENAME, 'CLERK' AS JOB, 7902 AS MGR, TO_DATE('19801217','yyyy-MM-dd') AS HIREDATE, 800 AS SAL, NULL AS COMM, 20 AS DEPTNO FROM DUAL UNION ALL
SELECT 7499 AS EMPNO, 'ALLEN' AS ENAME, 'SALESMAN' AS JOB, 7698 AS MGR, TO_DATE('19810220','yyyy-MM-dd') AS HIREDATE, 1600 AS SAL, 300 AS COMM, 30 AS DEPTNO FROM DUAL UNION ALL
SELECT 7521 AS EMPNO, 'WARD' AS ENAME, 'SALESMAN' AS JOB, 7698 AS MGR, TO_DATE('19810222','yyyy-MM-dd') AS HIREDATE, 1250 AS SAL, 500 AS COMM, 30 AS DEPTNO FROM DUAL UNION ALL
SELECT 7566 AS EMPNO, 'JONES' AS ENAME, 'MANAGER' AS JOB, 7839 AS MGR, TO_DATE('19810402','yyyy-MM-dd') AS HIREDATE, 2975 AS SAL, NULL AS COMM, 20 AS DEPTNO FROM DUAL UNION ALL
SELECT 7654 AS EMPNO, 'MARTIN' AS ENAME, 'SALESMAN' AS JOB, 7698 AS MGR, TO_DATE('19810928','yyyy-MM-dd') AS HIREDATE, 1250 AS SAL, 1400 AS COMM, 30 AS DEPTNO FROM DUAL UNION ALL
SELECT 7698 AS EMPNO, 'BLAKE' AS ENAME, 'MANAGER' AS JOB, 7839 AS MGR, TO_DATE('19810501','yyyy-MM-dd') AS HIREDATE, 2850 AS SAL, NULL AS COMM, 30 AS DEPTNO FROM DUAL UNION ALL
SELECT 7782 AS EMPNO, 'CLARK' AS ENAME, 'MANAGER' AS JOB, 7839 AS MGR, TO_DATE('19810609','yyyy-MM-dd') AS HIREDATE, 2450 AS SAL, NULL AS COMM, 10 AS DEPTNO FROM DUAL UNION ALL
SELECT 7788 AS EMPNO, 'SCOTT' AS ENAME, 'ANALYST' AS JOB, 7566 AS MGR, TO_DATE('19821209','yyyy-MM-dd') AS HIREDATE, 3000 AS SAL, NULL AS COMM, 20 AS DEPTNO FROM DUAL UNION ALL
SELECT 7839 AS EMPNO, 'KING' AS ENAME, 'PRESIDENT' AS JOB, NULL AS MGR, TO_DATE('19811117','yyyy-MM-dd') AS HIREDATE, 5000 AS SAL, NULL AS COMM, 10 AS DEPTNO FROM DUAL UNION ALL
SELECT 7844 AS EMPNO, 'TURNER' AS ENAME, 'SALESMAN' AS JOB, 7698 AS MGR, TO_DATE('19810908','yyyy-MM-dd') AS HIREDATE, 1500 AS SAL, 0 AS COMM, 30 AS DEPTNO FROM DUAL UNION ALL
SELECT 7876 AS EMPNO, 'ADAMS' AS ENAME, 'CLERK' AS JOB, 7788 AS MGR, TO_DATE('19830112','yyyy-MM-dd') AS HIREDATE, 1100 AS SAL, NULL AS COMM, 20 AS DEPTNO FROM DUAL UNION ALL
SELECT 7900 AS EMPNO, 'JAMES' AS ENAME, 'CLERK' AS JOB, 7698 AS MGR, TO_DATE('19811203','yyyy-MM-dd') AS HIREDATE, 950 AS SAL, NULL AS COMM, 30 AS DEPTNO FROM DUAL UNION ALL
SELECT 7902 AS EMPNO, 'FORO' AS ENAME, 'ANALYST' AS JOB, 7566 AS MGR, TO_DATE('19811203','yyyy-MM-dd') AS HIREDATE, 3000 AS SAL, NULL AS COMM, 20 AS DEPTNO FROM DUAL UNION ALL
SELECT 7934 AS EMPNO, 'MILLER' AS ENAME, 'CLERK' AS JOB, 7782 AS MGR, TO_DATE('19820123','yyyy-MM-dd') AS HIREDATE, 1300 AS SAL, NULL AS COMM, 10 AS DEPTNO FROM DUAL;
COMMIT;