MYSQL:如果变量不为空，如何根据变量将变量插入到表中？

SET @VARIABLE1 := 'Heyho';
create table Test(id integer, title varchar(100));
insert into Test(id, title) values(1, "Hello");
insert into Test(id, title) values(2, (SELECT @VARIABLE1));
insert into Test(id, title) values(3, (SELECT @VARIABLE2 WHERE @VARIABLE2 IS NOT NULL));
select * from Test;

id  title
1   Hello
2   Heyho
3   NULL

id  title
1   Hello
2   Heyho