MySQL Advanced II - Process Control Statement

1. MySQL process control statement - selection statement

1. There is only one judgment

delimiter $$;
create procedure p_showage(in age int)
begin
if age >= 18 then
  select '成年人';
else
  select '未成年人';
end if;
end
$$;

Modify the mysql end character;

delimiter ;

Set a variable;

set @age = 19;

Call the p_showage method;

call p_showage(@age);

2. Contains two judgments

delimiter $$;
create procedure p_showagetwo(in age int)
begin
if age >= 18 && age < 60 then
  select &#39;成年人&#39;;
elseif age >= 60 then
  select &#39;老年人&#39;;
else
  select &#39;未成年人&#39;;
end if;
end
$$;

2. MySQL process control statement-case control statement

create procedure p_addsaloary(in v_empno int)
begin
	declare adds int;
case v_empno
when 1 then
	set adds = 1;
when 2 then
	set adds = 2;
when 3 then
	set adds = 3;
else
	set adds = 4;
end case;
update test set age = adds where id = v_empno;
end;
$$;

ifnull(exp1,exp2) determines whether it is a null value. It has two parameters.

If the first expression is a null value, output the second value.

If the first expression The expression is not empty, and the first value is output

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