2 columns means 2 attributes , A relation R with two attributes then R will always in BCNF
let R (A,B)
1) A → B ⇒ BCNF (becoz A+={A,B}, A is super key )
2) B → A ⇒ BCNF (becoz B+={A,B}, B is super key )
3) A → B ,B → A ⇒ BCNF (here A and B are super key )
4) NO non trivial dependency ⇒ BCNF (becoz trivial FD's are always implied)