DQL Statements › Relationship Clauses › Combining Relationship Types › Deciding Which Type of Relationship to Use

Deciding Which Type of Relationship to Use

Sometimes the same relationship can be stated in either a chained or repeating fashion. Both types of relationships join unrelated tables. The following example demonstrates the use of both types of relationships to accomplish the same objectives.

Chained:
TABLE-A RELATED KEY1 TO TABLE-B RELATED KEY2 TO TABLE-C
Repeating:
TABLE-B RELATED KEY1 TABLE-A AND TABLE-B RELATED KEY2 TO TABLE-C

Some relationships can only be stated in a repeating fashion. For example:

TABLE-A RELATED KEY1 TABLE-B RELATED KEY2 TABLE-C AND TABLE-B
RELATED KEY3 TABLE-D

Whenever you have a table that joins two or more other tables, you must repeat the table name, hence the term repeating relationship.