Pathmaker Programming Guide

Appendix B How to Operate a DB Requester
Application
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This appendix provides a detailed explanation of how to operate a Pathmaker
application created with DB requesters and standard services. This information is of
interest to end users of such applications.
For the purpose of simplification, this appendix will refer only to NonStop SQL
terminologies. If the operation of the standard services differs significantly between
NonStop SQL tables and Enscribe files, it will be specifically noted. An Enscribe file is
equivalent to a NonStop SQL table, a record is equivalent to a row, a field equates to a
column, and an alternate key equates to an index.
Reading Rows The end user of a Pathmaker application created from DB requesters and standard
services can initiate a read of a row or group of rows in a table by requesting one of
several different types of read operations. These operations are:
READ FIRST (F4)
READ NEXT (F5)
READ APPROXIMATE (F6)
READ EXACT (F7)
READ GENERIC (F8)
READ MATCH (F9)
The end user initiates a read operation by positioning the cursor in a key column,
optionally typing in a value, and then pressing a function key associated with a read
operation. For most of the read operations, the application uses the value that was
entered to perform the read operation.
If the cursor is not positioned within a key column, the application functions as if the
first key column that appears on the screen was selected. For this reason, this key
column is sometimes called the default column.
If the application displays several boxes, the end user must position the cursor within
the desired box before a read operation is requested.
Note If the application developer has designated “Non-Index Reads” for a particular NonStop SQL table, the
end user will be able to perform any of the read operations using screen columns other than key columns.
This type of read tends to be much slower than a read using a key column.