r0 := UnboundTable: alltypes
  a int8
  b int16
  c int32
  d int64
  e float32
  f float64
  g string
  h boolean
  i timestamp
  j date
  k time

r1 := Selection[r0]
  selections:
    c: r0.c
    a: r0.a
    f: r0.f

a: r1.a