(** Common metaprogramming patterns for SQL syntax construction *)

val sqexps : env ::: {{Type}} -> fields ::: {Type} -> folder fields -> $(map sql_injectable fields)
             -> $fields -> $(map (sql_exp env [] []) fields)
(* Convert a record of Ur values into a record of SQL expressions *)

val selector : tn :: Name -> fs ::: {Type} -> ofs ::: {Type} -> [fs ~ ofs]
               => folder fs -> $(map sql_injectable fs) -> $fs
               -> sql_exp [tn = ofs ++ fs] [] [] bool
(* Build a boolean SQL expression expressing equality of some fields of a table
 * row with a record of Ur values *)

val joiner : tn1 :: Name -> tn2 :: Name -> fs ::: {Type} -> ofs1 ::: {Type} -> ofs2 ::: {Type}
             -> [[tn1] ~ [tn2]] => [fs ~ ofs1] => [fs ~ ofs2]
               => folder fs
               -> sql_exp [tn1 = ofs1 ++ fs, tn2 = ofs2 ++ fs] [] [] bool
(* Declare equality of same-named columns from two tables. *)