Ocaml merge Hash tables

I would like to merge two same-type hash tables in Ocaml, so that the information of both of them gets stored in a single table. Imagine, something like:

  type tabType = (string, variable) Hashtbl.t  let tabExample:tabType = Hashtbl.create 1000 in  let tab1 = do_stuff tabExample a true in  let tab2 = do_stuff tabExample a false in  let tabFinal = tab1@tab2

Any idea?