在mysql中創(chuàng)建函數(shù)的方法

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在mysql中可以通過語法“CREATE FUNCTION func_name ( [func_parameter] )”來創(chuàng)建函數(shù)，其中“CREATE FUNCTION”是用來創(chuàng)建函數(shù)的關(guān)鍵字。

在MySQL數(shù)據(jù)庫(kù)中創(chuàng)建函數(shù)(Function)

語法

CREATE FUNCTION func_name ( [func_parameter] ) //括號(hào)是必須的，參數(shù)是可選的
RETURNS type
[ characteristic ...] routine_body

CREATE FUNCTION 用來創(chuàng)建函數(shù)的關(guān)鍵字；

func_name 表示函數(shù)的名稱；

func_parameters為函數(shù)的參數(shù)列表，參數(shù)列表的形式為：[IN|OUT|INOUT] param_name type

IN：表示輸入?yún)?shù)；

OUT：表示輸出參數(shù)；

INOUT：表示既可以輸入也可以輸出；

param_name：表示參數(shù)的名稱；

type：表示參數(shù)的類型，該類型可以是MySQL數(shù)據(jù)庫(kù)中的任意類型；

RETURNS type：語句表示函數(shù)返回?cái)?shù)據(jù)的類型；

characteristic: 指定存儲(chǔ)函數(shù)的特性，取值與存儲(chǔ)過程時(shí)相同，詳細(xì)請(qǐng)?jiān)L問－MySQL存儲(chǔ)過程使用;

示例

創(chuàng)建示例數(shù)據(jù)庫(kù)、示例表與插入樣例數(shù)據(jù)腳本：

create database hr;
    use hr;
     
    create table employees
    (
    employee_id int(11) primary key not null auto_increment,
    employee_name varchar(50) not null,
    employee_sex varchar(10) default '男',
    hire_date datetime not null default current_timestamp,
    employee_mgr int(11),
    employee_salary float default 3000,
    department_id int(11)
    );
     
     
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('David Tian','男',10,7500,1);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Black Xie','男',10,6600,1);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Moses Wang','男',10,4300,1);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Rena Ruan','女',10,5300,1);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Sunshine Ma','女',10,6500,2);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Scott Gao','男',10,9500,2);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Warren Si','男',10,7800,2);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Kaishen Yang','男',10,9500,3);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Simon Song','男',10,5500,3);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Brown Guan','男',10,5000,3);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Eleven Chen','女',10,3500,2);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Cherry Zhou','女',10,5500,4);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Klause He','男',10,4500,5);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Maven Ma','男',10,4500,6);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Stephani Wang','女',10,5500,7);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Jerry Guo','男',10,8500,1);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Gerardo Garza','男',10,25000,8);
    insert into employees(employee_name,employee_sex,employee_mgr,employee_salary,department_id) values ('Derek Wu','男',10,5500,5);
select * from employees;

創(chuàng)建函數(shù)－根據(jù)ID獲取員工姓名與員工工資

DELIMITER //
CREATE FUNCTION GetEmployeeInformationByID(id INT)
RETURNS VARCHAR(300)
BEGIN
RETURN(SELECT CONCAT('employee name:',employee_name,'---','salary: ',employee_salary) FROM employees WHERE employee_id=id);
END//
DELIMITER ;

調(diào)用函數(shù)

在MySQL——函數(shù)的使用方法與MySQL內(nèi)部函數(shù)的使用方法一樣。

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