using Wanderer

DataSource = Dict(
    :a => [1, 2, 3, 4],
    :b => [2, 3, 4, 6],
    :c => [3, 4, 5, 6]
)

df = DataSource |>
       @select _, _.a + _.b + _.c => "a + b + c",
       @where _."a + b + c" !== missing,
       @groupby _."a + b + c" / _.a => key,
       @having key != 4.5,
       @orderby _.a |> length,
       @select sum(_."a + b + c") => sum, _.key => key,
       @limit 2

Dict{Symbol,Array{T,1} where T} with 2 entries:
  :key => [6.0, 4.0]
  :sum => [6, 28]