How to compare two columns in one table?

I would like to compare two columns in one table. I want to be able to return all rows where two columns have the same value.

I'm looking for something like SELECT * FROM FOO WHERE C1 = C4.

Therefore, in the example below, I would only return the first row:

C1    || C2  || C3  || C4
--------------------------
1     || a   || b   || 1
2     || a   || b   || 4
3     || b   || d   || 2
4     || b   || d   || 2

If that matters, I use SQLite(more specifically WebSQL).