Virtual tables are constructed of member tables, member fields, member keys and detailed relationship information to relate the member tables.
Member tables are the standard tables that are joined together to form a virtual table. A virtual table must contain at least one and no more than sixteen member tables.
A virtual table contains a primary table. All other member tables are joined to the primary table, whether directly or through another member table.
The virtual table must be granted read-access to all member tables. If a virtual table’s member table has been opened for exclusive use, and the virtual table is opened, an open table error will occur.
Member fields come from the member tables and become the virtual table fields.
Member keys provide access to the data in the virtual table. The member keys are selected from the primary table’s keys. The virtual table can add at most sixteen keys from the primary table. If a key contains a field that is not a member field of the table, the field will be added when the key is added.
By creating relationships between the fields, you relate the fields from one member table to another. A virtual table allows two relationship types: one-to-one and one-to-many.
A one-to-one relationship exists when a member table contains a record that corresponds to only one record in another member table. This type of relationship is created when the key used to join the two member tables is unique.
A one-to-many relationship exists when a member table contains a record that corresponds to more than one record in another member table. This type of relationship is created when the key used to join the two member tables is not unique.