Select from one table where id isn't in another table

I have two tables

table1
id
title

table2
id
table1_id

how can I find all items in the first table that don’t have their
“table1_id” in the second table?

In SQL I would do something like “select from table1 where id not in
(select table1_id from table2)”

Is there an easy way to do this in ruby?

Thanks in advance!
-Mike