Link table with more than one key?

[#1]

Hello and thanks for reading.

Suppose I have the following three tables:

How can I correctly join them through a link table? Should I use more than one? What I am doing is this:

1 ) Declare each key on each table:

TABLE1:

LOAD

     A & B     AS KEY_A_B,

     X

FROM TABLE1.QVD

TABLE2:

LOAD

     A & B                    AS KEY_A_B,

     A & B & C & D     AS KEY_A_B_C_D,

     Y

FROM TABLE2.QVD

TABLE3:

LOAD

     A & B                    AS KEY_A_B,

     A & B & C & D     AS KEY_A_B_C_D,

     Z

FROM TABLE3.QVD

2) Join them through one LINK TABLE

LINK_TABLE:

LOAD DISTINCT

     KEY_A_B,

     A,

     B

RESIDENT TABLE1

CONCATENATE

LOAD DISTINCT

     KEY_A_B,

     KEY_A_B_C_D,

     A,

     B,

     C,

     D

RESIDENT TABLE2

CONCATENATE

LOAD DISTINCT

     KEY_A_B,

     KEY_A_B_C_D,

     A,

     B,

     C,

     D

RESIDENT TABLE3

You can already guess what's going on here: If I proceed this way, I end up creating a synthetic key (of keys...) between my link table and TABLE1 and 2 (because they share KEY_A_B and KEY_A_B_C_D), so, how do I proceed in this case? Should I concatenate KEY_A_B and KEY_A_B_C_D into a single key? This sound really dirty and unnecessary complex. Should I use another LINK TABLE separately?

I would really appreciate your help on this matter. Thank you very much.