oracle 函数的用法(三)

-- 函数

1.oracle自带的标准函数 to_date,to_number
2.自定义函数

-- 自定义函数语法

1 CREATE OR REPLACE FUNCTION FUNCTION_name
2 [ (PARAMETERS [MODEL] datatype ... ) ]
3 RETURN datatype IS|AS
4 [local_variable_declarations ; ...]
5 BEGIN
6 -- action;
7 RETURN expression;
8 END [function_name];

-- 建立第一个函数 获取给定员工id的薪水

 1 CREATE OR REPLACE FUNCTION get_sal
 2 (
 3 ID employees.employee_id%Type
 4 )
 5 RETURN NUMBER IS
 6 sal employees.salary%TYPE := 0;
 7 BEGIN
 8 SELECT salary INTO sal FROM employees WHERE employee_id = ID;
 9 RETURN sal;
10 END get_sal; 

-- 执行方式

 1 -- 全局变量的方式执行
 2 VARIABLE salary NUMBER
 3 EXECUTE :salary := get_sal(100);
 4 -- 本地块的方式执行
 5 DECLARE sal employees.salary%TYPE;
 6 BEGIN
 7 sal := get_sal(100);
 8 END;
 9 --命令行执行
10 execute dbms_output.put_line(get_sal(100));
11 -- SQL语句执行
12 SELECT get_sal(100) FROM dual;

-- 函数在SQL语句中的使用 类似于avg count 等函数

1 CREATE OR REPLACE FUNCTION tax(VALUE IN NUMBER)
2 RETURN NUMBER IS
3 BEGIN
4 RETURN (VALUE * 0.08);
5 END;
6
7 SELECT tax(100) FROM dual;

函数的限制 ： 只接收in 类型的参数

-- 函数会犯的错误

 1 CREATE OR REPLACE FUNCTION dml_call_sql
 2 (
 3 sal NUMBER
 4 )
 5 RETURN NUMBER IS
 6 BEGIN
 7 INSERT INTO employees
 8 (employee_id,last_name,email,hire_date,job_id,salary)
 9 VALUES
10 (1,‘forst‘,‘[email protected]‘,SYSDATE,‘sa_man‘,sal);
11 RETURN (sal + 100);
12 END;
13
14 UPDATE employees SET salary = dml_call_sql(2000) WHERE employee_id = 170;

报错 ： update，insert中不能调用 有insert 的函数

-- 删除一个函数

1 drop function function_name

-- function 的数据字典

1 SELECT text FROM user_source WHERE TYPE=‘FUNCTION‘ ORDER BY line; -- 显示函数内容

2 SELECT object_name FROM user_objects WHERE object_type=‘FUNCTION‘; -- 显示函数

-- user_objects对象的结构 

 1 SQL> desc user_objects;
 2 Name           Type          Nullable Default Comments
 3 -------------- ------------- -------- ------- ----------------------------------------------------------------------------
 4 OBJECT_NAME    VARCHAR2(128) Y                Name of the object
 5 SUBOBJECT_NAME VARCHAR2(30)  Y                Name of the sub-object (for example, partititon)
 6 OBJECT_ID      NUMBER        Y                Object number of the object
 7 DATA_OBJECT_ID NUMBER        Y                Object number of the segment which contains the object
 8 OBJECT_TYPE    VARCHAR2(19)  Y                Type of the object      -- 类型 function， procedure  等
 9 CREATED        DATE          Y                Timestamp for the creation of the object
10 LAST_DDL_TIME  DATE          Y                Timestamp for the last DDL change (including GRANT and REVOKE) to the object
11 TIMESTAMP      VARCHAR2(19)  Y                Timestamp for the specification of the object
12 STATUS         VARCHAR2(7)   Y                Status of the object    -- 无效状态的在数据库巡检时抓出来 重新编译
13 TEMPORARY      VARCHAR2(1)   Y                Can the current session only see data that it place in this object itself?
14 GENERATED      VARCHAR2(1)   Y                Was the name of this object system generated?
15 SECONDARY      VARCHAR2(1)   Y                Is this a secondary object created as part of icreate for domain indexes?
16 NAMESPACE      NUMBER        Y                Namespace for the object
17 EDITION_NAME   VARCHAR2(30)  Y                Name of the edition in which the object is actual                            

-- 无效对象重新编译脚本  【扩展知识】

D:\oracle11g\app\Administrator\product\11.2.0\dbhome_1\RDBMS\ADMIN

utlrp.sql脚本文件 

函数和存储过程的异同