induction sch with
| nil => simp [List.map, List.append]
| cons s ss ih =>
  simp only [List.map]
  rw [ih]
  simp [List.append]
  exact dropColumn t _
η : Type u_η
dec_η : DecidableEq η
sch : Schema
τ : Type u
inst : DecidableEq τ
t : Table sch
c : η
vs : List (Option τ)
⊢ List.map Prod.fst (Schema.append sch [(c, τ)]) = List.map Prod.fst sch ++ [c]
no goals