I have tried this code:

def my_func(params) do
  ...
  |> select(
        [l],
        %{
          date: fragment("date_trunc('?',?) as date",
            ^params.date_trunc_type,
            l.inserted_at),
        }
      )
  ...
  |> Repo.all()
end

But i’m stacked at this error:

** (Postgrex.Error) ERROR 42P18 (indeterminate_datatype) could not determine data type of parameter $1

query: SELECT date_trunc('$1',s0."inserted_at") as date...

My Modules:

defmodule Administration.Reports.Params do
  ...

  alias Administration.Enum.DateTruncType
  embedded_schema do
    ...
    field :date_trunc_type, DateTruncType, default: :month
  end
  
  ...
end

defmodule Administration.Enum.DateTruncType do
  use EctoEnum,
    hour: "hour",
    day: "day",
    month: "month",
    year: "year"
end

I want to construct this sql’s SELECTs

SELECT date_trunc('hour', inserted_at)
SELECT date_trunc('day', inserted_at)
SELECT date_trunc('month', inserted_at)
SELECT date_trunc('year', inserted_at)