let bar x = PROJECT [Foo_a, Foo_b] x

let selection z x = PROJECT [Foo_whatever] (SELECT [Foo_name = z] x)

let foo b c = b + c

let selection2 a b c x =
  SELECT
    [Foo_name = a AND (Foo_whatever < Foo_something OR Foo_something >= foo b c)]
    x

module Opaque : sig
  type whatever_id
  val encode_whatever_id : whatever_id -> string
  val decode_whatever_id : string -> whatever_id
end =
struct
    type 'a opaque_int = int
    type whatever_id = [`Whatever_id] opaque_int
    let encode_whatever_id = string_of_int
    let decode_whatever_id = int_of_string
end

include Opaque

TABLE user users
    COLUMN id SERIAL AUTO PRIMARY KEY
    COLUMN name VARCHAR(64)
    COLUMN age INT NULLABLE
    COLUMN whatever_id INT(whatever_id) FOREIGN(whatever, id)
    COLUMN nickname VARCHAR(64) DEFAULT "baka"
END

let table :
      ([`Foo_name of string | `Foo_whatever of int
       | `Foo_something of int | `Foo_a of bool | `Foo_b of float],
       [`Foo_name | `Foo_whatever | `Foo_something
        | `Foo_a | `Foo_b ]) Relational.relation =
  Relational.table "foo"
    { Relational.value_to_sql =
        (function
             `Foo_name s -> s
           | `Foo_whatever i | `Foo_something i -> string_of_int i
           | `Foo_a b -> string_of_bool b
           | `Foo_b f -> string_of_float f);
      value_of_sql =
        (fun t isnull s -> match t with
             `Foo_whatever -> `Foo_whatever (int_of_string s)
           | `Foo_something -> `Foo_something (int_of_string s)
           | `Foo_name -> `Foo_name s
           | `Foo_a -> `Foo_a (s = "true")
           | `Foo_b -> `Foo_b (float_of_string s))
    }
    ["name"; "whatever"; "something"; "a"; "b"]

let foo2 = SELECT [Foo_foo = "bar"] (RENAME [Foo_name AS Foo_foo] table)

let foo3 = ORDER [Foo_foo] foo2

let foo4 = ORDER [Foo_name DESC] table

let foo5 y = PRODUCT [Foo_foo] [Foo_bar] foo3 y

let () =
  let disp x = print_endline (Relational.to_sql x) in
    disp (bar table);
    disp (selection "Koshimizu Haruna" table);
    disp (selection2 "Jung" 12 12 table);
    disp foo3