A tree structure can readily be represented using indexes. The technique is to store each one-to-many relationship as an index. These lists are then used to match parents and children.
Using the VENDOR and INVOICE records in Figure H-19, we see that VENDOR AA (in RRN1) owns IN-VOICEs 110 (RRN7) and 118 (RRN3). Thus, RRN1 is the parent of RRN7 and RRN3. We can represent this fact with the index in Figure H-24. The list simply associates a parent’s address with the addresses of each of its children.
If the tree has several 1:N relationships, several indexes will be required—one for each relationship. For example, for the structure in Figure H-13, five indexes are needed.