Calling stored procedures in mysql, definition of variables,

1. Calling stored procedure

1. Its essence is to put some sql The process of encapsulating statements into fixed blocks of code is similar to c Functions in language .

for example ： The following is to encapsulate into fixed code blocks

create procedure proc01()
begin
 select empno,ename from emp;
end $$
delimiter;

2. Calling stored procedure ：

call Defined process name
for example ：

call proc01();

2. Statement / Defining variables ( User variables , Global variables , Session variables )

1. Definition / Declare variables ;

declare var_name01 varchar(20) default 'aaa';

Using stored procedures to change declared variables

delimiter $$
create procedure proc02()
begin
declare var_name01 varchar(20) default 'aaa'; --  Statement / Defining variables 
set var_name01 = 'shangsan';
select var_name01;
end $$
delimiter;
call proc02();

2. Define user variables ;

@var_name01;
for example ：

delimiter $$
create procedure proc04()
begin
set  @var_name01 = ' Beijing ';
end $$
delimiter;
call proc04();
select @var_name01;

3. Define global variables ：

@@global.var_name

--  View global variables 
show global variables;
--  View a local variable 
select @@global.auto_increment_increment;
--  Modify global variables 
set global sort_buff_size = 50000;
set @@global.sort_buff_size = 50000;

4. Define session variables

The usage is similar to global variables and user variables

@@session.var_name

Works only in the current session

3. keyword in,out,inout Use

in

delimiter $$
create procedure proc06(in param_empno int)
begin
select * from emp where empno = param_empno;
end $$
delimiter;
call proc06(1001);

delimiter $$
create procedure proc07(in dname varchar(50), in sal decimal(7,2))
begin
select * from dept a,emp b where a.deptno = b.deptno and a.dname = dname and b.sal = sal;
end $$
delimiter;
call proc07(' Department of science and Engineering ',20000);

out keyword ：

delimite $$
create procedure proc08(in in_empno int,out out_name varchar(50))
begin 
 select ename into out_ename from emp where empno = in_empno;
 end $$
 delimiter;
call proc08(1001,@o_ename);
select @o_ename;

inout keyword ：

-- inout
delimiter $$
create procedure proc10(inout num int)
begin
set num = num * 10;
end $$
delimiter ;
set @inout_num = 3;
call proc10(@inout_num);
select @inout_num;

--  Incoming employee name , Splicing department number , Transfer in salary , Find out the annual salary 
delimiter $$
create procedure proc11(inout ename varchar(50),inout sal int)
begin
select concat_ws('_',deptno,ename) from emp where emp.ename = ename;
set sal = sal * 12;
end $$
delimiter;
set @inout_name=' Guan yu ';
set @inout_sal = 3000;
call proc11(@inout_name,@inout_sal);
select @inout_sal;
select@inout_name;

4. Judgment in stored procedures

--  control - Judge 
--  grammar 
/*[elseif search condition 2 then statement list 2] [else statement list n] end if*/


--  Case study 1
--  Enter student's grade , To judge the level of achievement 
delimiter $$
create procedure proc_12_if(in score int)
begin
	if score <60
	 then
		select  ' fail, ';
	elseif score>=60 and score<80
	 then
		select' pass ';
	elseif score>=80 and score<90
	 then
		select ' good ';
	elseif score>=90 and score<100
	 then 
		select ' good ';
	elseif score>100
	 then 
		select ' error ';
	end if;
end $$
delimiter ;
set @score = 55;
call proc_12_if(@score);

delimiter $$
create procedure proc_13_if(in in_name varchar(20))
begin
declare var_sal decimal(7,2);
declare result varchar(20);
seelct sal into var_sal from emp where ename = in_name;
if var_sal<10000
	then 
		set result = ' Probationary salary ';
elseif var_cal < 20000
	then 
		set result = ' Salary for regular employment ';
else
	set result = ' Veteran salary ';
end if;
end $$
delimiter ;
--  call ：
call proc_13_if(' Guan yu ')



--  Flow control statement ：case
delimiter $$
create procedure proc14_case( in pay_type int)
begin
	case pay_type
		when 1 then select' Wechat payment ';
		when 2 then select' Alipay pay ';
		when 3 then select' Bank card payment ';
		else select ' Other payment methods ';
		end case;
end $$
delimiter;
call proc14_case(2);

--  Format 2
delimiter $$
create procedure proc_14_case(in score int)
begin
case
	when score <60
	 then
		select  ' fail, ';
	when score>=60 and score<80
	 then
		select' pass ';
	when score>=80 and score<90
	 then
		select ' good ';
	when score>=90 and score<100
	 then 
		select ' good ';
	when score>100
	 then 
		select ' error ';
	end case;
end $$
delimiter ;

5. Loops in stored procedures ：

--  loop :
create table user(
 uid int primary key,
 username varchar(50),
 password varchar(50)
 );

delimiter $$
create procedure proc16_while(in insertCount int)
begin
	declare i int default 1;
	lable: while i<=insertCount do
		insert into user(uid,username,password) values (i,concat('user-',i),'123456');
		set i = i+1;
	end while lable;
end $$
delimiter;

call proc17_while_leave(10);


-- while+leave
truncate table user;



delimiter $$
create procedure proc17_while_leave(in insertCount int)
begin
	declare i int default 1;
	lable: while i<=insertCount do
		insert into user(uid,username,password) values (i,concat('user-',i),'123456');
		
		if i = 5 then
			leave lable;
			end if;
			set i = i+1;
	end while lable;
end $$
delimiter;


-- while + iterate  Skip this cycle , Make the next cycle 

delimiter $$
create procedure proc18_while_iterate(in insertCount int)
begin
	declare i int default 1;
	lable: while i<=insertCount do
		insert into user(uid,username,password) values (i,concat('user-',i),'123456');
		set i = i+1;
		if i = 5 then
			iterate lable;
			end if;
			
	end while lable;
end $$
delimiter;




-- repeat




delimiter $$
create procedure proc18_repeat(in insertCount int)
begin
	declare i int default 1;
	lable: repeat
		insert into user(uid,username,password) values (i,concat('user-',i),'123456');
		set i = i+1;
		until i>insertCount
	end repeat lable;
end $$
delimiter;
call proc18_repeat(10);



-- loop loop 
delimiter $$
create procedure proc19_loop(in insertCount int)
begin
declare i int default 1;
label:loop
	insert into user(uid,username,password) values (i,concat('user-',i),'123456');
	set i = i+1;
	if i>insertCount
		then
			leave label;
	end if;
end loop label;
end $$
delimiter;
call proc19_loop(10);

6. Cursors in stored procedures

--  The cursor (cursor)
--  declare cursor 
--  Open cursor 
--  Get value through cursor 
--  Close cursor 


delimiter $$
create procedure proc_18_cursor(in in_dname varchar(50))
begin
--  Defining local variables 
declare var_empno int;
declare var_ename varchar(50);
declare var_sal decimal(7,2);
--  declare cursor 
declare my_cursor cursor for 
select empno,ename,sal
from dept a, emp b
where a.deptno = b.deptno and a.dname = in_dname;
--  Open cursor 
open my_cursor;
--  Get value through cursor 
label: loop
fetch my_cursor into var_empno,var_ename,var_sal;
select var_empno,var_ename,var_sal;
end loop label;
--  Close cursor 
close my_cursor;
end $$
delimiter;

call proc19_cursor();

7. Exception handling in storage structures ：

delimiter $$
create procedure proc_21_cursor_handler(in in_dname varchar(50))
begin
--  Defining local variables 
declare var_empno int;
declare var_ename varchar(50);
declare var_sal decimal(7,2);
--  Define tag values ：
declare flag int default 1;
--  declare cursor 
declare my_cursor cursor for 
select empno,ename,sal
from dept a, emp b
where a.deptno = b.deptno and a.dname = in_dname;


--  Define handle ： Define how to handle exceptions 
/* 1. How the program should execute after exception handling  continue : Continue with the remaining code  exit : Directly terminate the program  2. The trigger condition ：  Condition code ：  Condition name ： SQLWARNING NOT FOUND SQLEXCEPTION 3. What code is executed after the exception is triggered ：  Set up flag Value --- > 0 */
	declare continue handler for 1329 set flag = 0;
--  Open cursor 
open my_cursor;
--  Get value through cursor 
label: loop
fetch my_cursor into var_empno,var_ename,var_sal;
-- 
if flag = 1 then
select var_empno,var_ename,var_sal;
else 
leave label;
end loop label;
--  Close cursor 
close my_cursor;
end $$
delimiter;

call proc21_cursor();