How can I perform part of raw creating in ruby on rails?

for example:

My table is:

create table aaa {
    a int not null auto_increment,
    b int not null,
    c varchar(255),
    primary key (a,b)
}

Now, I want to insert a record

insert into aaa values (a,b,c) 
    ((SELECT * from (select IFNULL(MAX(a)+1,1) as temp FROM aaa where b = 2) as P),
      2,"what ever";

How can I achieve this?

The only solution I found is to make all of this become raw query in this page.

Can I write this something like that:

reault = Aaa.create({a: "(SELECT * from (select IFNULL(MAX(a)+1,1) as temp FROM aaa where b = 2) as P)", b: 2, c:"what ever"})

Only field a is used raw query and other part is wrote as usual?

rails: 4.2.1 DB gem is Mysql2