Changing relationships
After you have created a relationship, you can add or change match fields, change relational operators, and set options for creating, deleting, and sorting related records.
Note  You can’t change tables within a relationship. You must create a new relationship.
To change a relationship:
Open the relationships graph for the database.
See Working with the relationships graph.
You can also select the relationship in the relationships graph and click Edit button.
Select a new relational operator from the list and click Change.
Allow creation of records in this table via this relationship. When this option is selected, entering data in a related field that has no corresponding related record creates a related record based on the match field in the current table.
Delete related records in this table when a record is deleted in the other table. This option deletes related records even when you're browsing a layout that doesn't display the related records.
Note  When this option is selected in multiple relationships in the same database, deleting a record from one table can also delete related records in other related tables for which the option has been enabled. This is called a cascading delete. You should consider this option carefully before enabling it.
Sort records. Then, in the left list in the Sort Records dialog box, double-click the fields to sort. To change the order in which fields are sorted, drag fields in the right list into the order you want. Select other options, then click OK.
To change the sort order, click Specify in the Edit Relationship dialog box.
Select Sort records to display the first found record in a particular sort order (such as the lowest or highest value) when you have one related field directly on a layout of the current table. (For example, display the most recent check-out date for a particular piece of equipment.) Also sort related records to access multiple records that are in a particular sort order and display them in a portal.
When Sort records is selected and data in a related field in a portal changes, the portal records are re-sorted whenever the relationship is re-established. (For example, records re-sort when you browse out of and then back into the record, or change the value in the match field.)
Related topics 
About relationships
About planning a database
About the types of relationships
About match fields for relationships
Creating relationships
Adding tables to the relationships graph