Table3 { (int id, int type) PK }
Table1 { (int id, int type [CHECK type = 1]) FK Table3 }
Table2 { (int id, int type [CHECK type = 2]) FK Table3 }

Table4 { (int id, int type [CHECK type IN (1,2)]) PK }
Table1 { (int id, int type [CHECK type = 1]) FK Table4 }
Table2 { (int id, int type [CHECK type = 2]) FK Table4 }
Table3 { (int id, int type) FK Table4 }

TABLE_A:
    PK_FIELD int NOT NULL
    OTHER_FIELD int NOT NULL, NOT IN TABLE_B.OTHER_FIELD

TABLE_B:
    PK_FIELD int NOT NULL
    OTHER_FIELD int NOT NULL, NOT IN TABLE_A.OTHER_FIELD

TABLE_C:
    PK_FIELD int NOT NULL
    OTHER_FIELD int NOT NULL IN (TABLE_A.OTHER_FIELD OR TABLE_B.OTHER_FIELD