Do i need to change code in rails when i migrate database from sqlite to Postgresql or someother

I am new to ruby on rails framework and build some Blogs,portfolio like applications using rails.For that i used sqlite as my database. I would like to create a scalable applications and though sqlite is a lightweight database. I would like to change the database as postgresql , Mysql and mongodb etc.

So my question is if i change the database ,did i need to change rails code or it will be same as using sqlite?