MySQL 建立函數(Function)

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目標

怎麼樣MySQL建立資料庫功能(Function)

文法

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

• CREATE FUNCTION 用來建立函數的keyword；
• 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：表示既能夠輸入也能夠輸出；
4. param_name：表示參數的名稱；
5. type：表示參數的類型，該類型能夠是MySQL資料庫中的隨意類型；

• RETURNS type：語句表示函數返回資料的類型；
• characteristic: 指定儲存函數的特性，取值與預存程序時同樣，具體請訪問－MySQL預存程序使用;

示範範例

建立示範範例資料庫、示範範例表與插入範例資料指令碼：

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;

建立函數－依據ID擷取員工姓名與員工工資

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

調用函數

在MySQL——函數的用法與MySQL內建函式的用法一樣。

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MySQL 建立函數(Function)