>>Thank you Hilmar for this improvment ! I suppose that BINTOC will not preserve the order for sorting (at least, the doc doesn't say that it preserves the order) - but that is probably unimportant in my case.

>I think it will, because of the binary representation. I am not sure about negative numbers.

OK, to be tested then !

>But you must be careful to use only "Machine" for the collation sequence. "Machine" is already the default, but you may have changed this.

>bintoc() will accept the entire range of a 4 byte integer, i.e., from minus to plus 2 thousand million, approximately.

Thank you for these details. This solution seems to be as close as one can get to a real composite key.