具有动态变量的存储过程

Question

我正在从 YouTube 学习 MySQL。我处于初级水平。我想知道为什么我们使用 @F_emps 。 这里

创建新表

create table employees_detailss (
    Emp_id int primary key, 
    Emp_name varcharacter (28), 
    Age int, 
    Gender character (10), 
    Department varcharacter (25), 
    City character (22), 
    salary float
);

以了解如何向表元素

describe employees_details ; 

插入值

Insert into employees_detailss
values 
( 5524, "Jimmie Clayton", 44,"M", "Marketing", "Berlin", 35000),
(2174,  "Clyde Turner", 34, "F" , "Finance", "Paris",   23000),
(4141,  "Carol Hubbard" , 37, "M",  "IT","Rome", 45000),
(6182,  " Dennis Flores" , 45, "M",  "Supply chain", " Venis", 28000),  
(5324,  "Stewart Bowers", 47 , "F" ,  "IT", " London" ,  50000),    
(7446,  "Nichole Bush", 27, "M" ,"Marketing", "Lisbon", 20000),
(965,   "Anne Brady",   32, "F",  "Finance", "Berlin",28000),   
(6177,  "Kristina Riley",36,"F", "Supply chain", "Milan", 34000),   
(4855,  "Evan Martin",  34,"M",  "Finance", "Soest",29000),
(5899,  "Josephine Mason", 47, "M",  "IT", "Dresden", 44000),
(1994,  "Manuel Houston",33,"F", "Marketing", "Munich", 42000),
(387,   "Robyn Fernandez", 27, "M",  "Finance", "Postdam",40000),
(2125,  "Bessie Richardson", 35, "F",  "IT", "Hamburg", 34000),
(8180,  "Christie Henderson", 33, "F", "Marketing", "Cottbus", 44000);

select * from employees_detailss ;

delimiter //
create Procedure Sp_CountEmployeesss ( out Total_emps int )
begin 
select count(Emp_name) into Total_emps from employees_detailss
where Gender = "F";
end //
delimiter ;

call Sp_CountEmployeesss(@F_emps);
select @F_emps as Female_Emps;

Answer 1

当您进行调用时：

call Sp_CountEmployeesss(@F_emps);
select @F_emps as Female_Emps;

这意味着您将一个变量传递给 Sp_CountEmployeesss 来存储结果。然后，在调用行之后，数据将保存在 @F_emps 中，因此您将执行选择来查询结果并查看计算的数据。