Pathmaker Programming Guide

Creating a DB Requester Application
Pathmaker Application Development Overview
3–26 067868 Tandem Computers Incorporated
Multifile applications and any single-file applications that display several repetitions
of a record use the cursor position to determine to which box or record an operation
applies.
Note If you are creating a multifile DB requester that accesses two tables that have a many-to-many
relationship, you must use the Pathmaker Record Instance Detail screen to describe the relationship
table, even if columns from the relationship table will not appear on the screen.
Choosing a Parent and Child. To decide which file is to be a parent and which file is to be
a child, consider the purpose of the application. There are two requirements regarding
this choice:
The link field of a child must be one of the following:
A primary key field
An alternate key field (index)
The leading portion of a primary key or alternate key field (index)
Note For NonStop SQL tables only, if nonindex reads have been allowed for a child, the link column does not
have to be a primary key or index column.
The size and type of the link field for the parent must be identical to the size and
type of the link field of the child.
Refer to Appendix B of this manual for more information about these requirements.
Multifile DB Requester Layout Options. The screen displayed by a multifile DB requester
application reflects the parent-child relationships you define. You can choose between
two possible arrangements of parent and child boxes on the default screen. In the first,
the application displays a child box after the link field of the parent box. If any other
fields in the parent box follow the link field, the application displays these fields below
the child box. Figure 3-9, shown previously, is an example of this arrangement.
Alternatively, the application can display a child box after the last field of its parent
box. Figure 3-10 illustrates this arrangement.
A DB requester application with either arrangement does not display the link field of a
child box because the data in this field is identical to the data in the link field of its
parent box.