Associations

An association is a set of two or more multivalued fields that are related such that the values are inter-dependent. For example, an order processing database might contain a file listing the items in each order. This would require a multivalued list of products and a corresponding multivalued list of quantities. A realistic data file may contain several associated sets of fields.

The query processor needs to know about this relationship. An association is defined by giving it a name which appears in field 7 of the dictionary entry of each field in the association. There is also a phrase record with this name which contains a space separated list of the fields that make up the association.

Thus, starting from any one element of the association, its dictionary entry can be used to find the phrase record which, in turn, allows the query processor to find all the members of the association.

For compatibility with some other multivalue database products, the ASSOC.UNASSOC.MV mode of the OPTION command can be used to make the query processor treat all multivalue fields that are not in defined associations as being associated together.