drop table if exists test;
create table test(
id int
);
insert into test(id) values(1), (2);

create table test_trigger(
id int
);
insert into test_trigger(id) values(1);

delimiter $$
create trigger test_t2 after update on test for each row
begin
update test_trigger set id = 3 where id = 1;
end
$$
delimiter ;

delimiter $$
drop function if exists say ;
create function say() returns varchar(20)
begin
return ‘hello world‘;
end
$$
delimiter ;

select say();

delimiter $$
create function say2(name varchar(10)) returns varchar(20)
begin
return concat(‘hello world, ‘, name);
end
$$
delimiter ;

select say2(‘Mr‘);

if xxx then
xxx
elseif xxx then
xxx
else
xxx
end if;

delimiter $$
create function func1() returns varchar(20)
begin
set @cur_h = hour(now());
if @cur_h >= 18 then
return ‘night‘;
elseif @cur_h > 12 then
return ‘afternoon‘;
else
return ‘morning‘;
end if;
end
$$
delimiter ;

delimiter $$
create function func2() returns int
begin
set @i = 1;
set @sum = 0;
while @i <= 10 do
set @sum = @sum + @i;
set @i = @i + 1;
end while;
return @sum;
end
$$
delimiter ;

delimiter $$
create function func3() returns int
begin
set @i = 1;
set @sum = 0;
w: while @i <= 10 do
if @i = 5 then
leave w;
end if;
set @sum = @sum + @i;
set @i = @i + 1;
end while w;
return @sum;
end
$$
delimiter ;

delimiter $$
create function func4() returns int
begin
set @i = 1;
set @sum = 0;
w: while @i <= 10 do
if @i = 5 then
set @i = @i + 1;
iterate w;
end if;
set @sum = @sum + @i;
set @i = @i + 1;
end while w;
return @sum;
end
$$
delimiter ;

repeat
....
until xxx   -- 这里没有 ‘;‘ 号
end repeat;

delimiter $$
drop function if exists my_sum;
create function my_sum(start_num int, end_num int) returns int
begin
declare i int default start_num;
set i = 3;                  -- 报错, 要先声明完, 之后才能定义, 这里先定义了
declare sum int default 0;
w: while i <= end_num do
set sum = sum + i;
set i = i + 1;
end while w;
return sum;
end
$$
delimiter ;

delimiter $$
drop function if exists my_sum;
create function my_sum(start_num int, end_num int) returns int
begin
declare i int default start_num;
declare sum int default 0;
w: while i <= end_num do
set sum = sum + i;
set i = i + 1;
end while w;
return sum;
end
$$
delimiter ;

delimiter $$
create procedure p1(n int)
begin
select n;
end
$$
delimiter ;

call p1(‘abc‘);

delimiter $$
create procedure p2(in n int)
begin
select n;
end
$$
delimiter ;

call p2(‘abc‘);

delimiter $$
create procedure p3(out n int)
begin
set n = 3;
end
$$
delimiter ;

call p3(@ans);
select @ans;

set @ans = 0;
delimiter $$
create procedure p4(inout n int)
begin
set n = 3;
end
$$
delimiter ;

call p4(@ans);
select @ans;                    -- 3

drop table if exists goods;
create table goods (
id int,
num int,
name varchar(20)
);

insert into goods (id, num, name) values
(1, 10, ‘one‘),
(2, 20, ‘two‘),
(3, 30, ‘thr‘);


delimiter $$
drop procedure if exists p5;
create procedure p5()
begin
select * from goods;
end
$$
delimiter ;

call p5();

delimiter $$
drop procedure if exists p6;
create procedure p6()
begin
declare row_id int;
declare row_num int;
declare row_name varchar(20);
declare getgoods cursor for select * from goods;
open getgoods;
fetch getgoods into row_id, row_num, row_name;
select row_id, row_num, row_name;

fetch getgoods into row_id, row_num, row_name;
select row_id, row_num, row_name;

close getgoods;
end
$$
delimiter ;

call p6();

delimiter $$
drop procedure if exists p7;
create procedure p7()
begin
declare row_id int;
declare row_num int;
declare row_name varchar(20);
declare i   int default 0;
declare cnt int default 0;

declare getgoods cursor for select * from goods;
select count(*) from goods into cnt;
open getgoods;

while i < cnt do
   fetch getgoods into row_id, row_num, row_name;
   select row_id, row_num, row_name;
   set i = i + 1;
end while;
close getgoods;
end
$$
delimiter ;

call p7();

-- 报错, 要先定义 游标变量, 然后定义 end_of_cursor 最后定义 handler...
-- ERROR 1337 (42000): Variable or condition declaration after cursor or handler declaration
delimiter $$
drop procedure if exists p8;
create procedure p8()
begin
declare row_id int;
declare row_num int;
declare row_name varchar(20);
declare getgoods cursor for select * from goods;
declare end_of_cursor int default 0;
declare continue handler for not found set end_of_cursor = 1;

open getgoods;

while end_of_cursor = 0 do
    fetch getgoods into row_id, row_num, row_name;
    select row_id, row_num, row_name;
end while;
close getgoods;
end
$$
delimiter ;

call p8();

-- 会多取一次
delimiter $$
drop procedure if exists p8;
create procedure p8()
begin
declare row_id int;
declare row_num int;
declare row_name varchar(20);
declare end_of_cursor int default 0;
declare getgoods cursor for select * from goods;
declare continue handler for not found set end_of_cursor = 1;
open getgoods;

repeat
fetch getgoods into row_id, row_num, row_name;
select row_id, row_num, row_name;
until end_of_cursor = 1
end repeat;
close getgoods;
end
$$
delimiter ;

call p8();

delimiter $$
drop procedure if exists p9;
create procedure p9()
begin
declare row_id int;
declare row_num int;
declare row_name varchar(20);
declare end_of_cursor int default 0;
declare getgoods cursor for select * from goods;
declare continue handler for not found set end_of_cursor = 1; -- 判断到最后
open getgoods;

while end_of_cursor = 0 do
    fetch getgoods into row_id, row_num, row_name;
    if end_of_cursor != 1 then      -- 不加这句话会多取一次, 上面的 handle 表示判断到最后还是 continue
        select row_id, row_num, row_name;
    end if;
end while;
close getgoods;
end
$$
delimiter ;

call p9();

delimiter $$
drop procedure if exists p10;
create procedure p10()
begin
declare row_id int;
declare row_num int;
declare row_name varchar(20);
declare end_of_cursor int default 0;
declare getgoods cursor for select * from goods;
declare exit handler for not found set end_of_cursor = 1; -- 判断到了最后, 后面的代码不再继续执行
open getgoods;

while end_of_cursor = 0 do
    fetch getgoods into row_id, row_num, row_name;
    select row_id, row_num, row_name;
end while;
close getgoods;
end
$$
delimiter ;

call p10();