MySQL -- 創建函數(Function

目標

如何在MySQL數據庫中創建函數(Function)

 

語法

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

• CREATE FUNCTION 用來創建函數的關鍵字；
• func_name 表示函數的名稱；
• func_parameters為函數的參數列表，參數列表的形式為：[IN|OUT|INOUT] param_name type

1. IN：表示輸入參數；
2. OUT：表示輸出參數；
3. INOUT：表示既可以輸入也可以輸出；
4. param_name：表示參數的名稱；
5. type：表示參數的類型，該類型可以是MySQL數據庫中的任意類型；

• RETURNS type：語句表示函數返回數據的類型；
• characteristic: 指定存儲函數的特性，取值與存儲過程時相同，詳細請訪問－MySQL存儲過程使用;

 

示例

創建示例數據庫、示例表與插入樣例數據腳本：

 

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;

 

 

創建函數－根據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 ;

 

 

調用函數

在mysql——函數的使用方法與MySQL內部函數的使用方法一樣。