Mysql process control (if, while, repeat, loop)

1. Process control

1. Conditional statement: if

delimiter %%%
create procedure p01(in num int)
begin
    if num = 1 then
        select 1;
    elseif num = 2 then
        select 2;
    else select 3;
    end if;
end %%%
delimiter ;

2. Loop statement

• while loop

delimiter %%%
create procedure p02()
begin
    declare num int;
    set num = 0;
    while num < 3 do
        select num;
        set num = num + 1;
    end while;
end %%%
delimiter ;

• repeat loop

delimiter %%%
create procedure p03()
begin 
    declare num int;
    set num = 0;
    repeat
        select num;
        set num = num + 1;
        until num > 3  # 结束条件:当num>3时结束
    end repeat;
end %%%
delimiter ;

• loop circulation

delimiter %%%
create procedure p04()
begin
    declare num int default 0;
    myloop:loop
        set num=num+1;
        if num>=3 then
            leave myloop;  # 当 num>=3 结束循环
        end if;
        select num;
    end loop myloop;
end %%%
delimiter ;

—end—