OpenEdge Data Management: DataServer for Microsoft SQL Server

Chapter 2: Initial Programming Considerations
MS SQL Server data source views
MS SQL Server data source schema objects include views. A view is a presentation of
data in one or more tables. Views appear as tables, not as views, in the Data
Dictionary’s table list for the schema holder. In addition, the schema holder contains no
unique index information for views. Because views do not have unique indexes, you
cannot modify any of the data that a view contains; however, you can access a view
with the FOR EACH, FIND NEXT, and GET NEXT OpenEdge statements. Furthermore,
because views do not have index definitions, the DataServer cannot reposition the
cursor to retrieve individual records. Thus, you must be sure to get all of the data that
you need in a single database request.
The following ABL code example retrieves data from a view:
OPEN QUERY query-name FOR EACH view-name.
REPEAT:
GET NEXT query-name.
DISPLAY view-name.
. . .
END.
If a view has a unique combination of columns, you can simulate a unique index using
the Data Dictionary. You can then access a view that has a simulated unique index just
as you do a table; that is, you can scroll backward and forward, and update, create, and
delete data. See the “Modifying field-level information” section on page 309 for
information on how to do this.
Some views are the results of joins and contain data from more than one table. You
can also provide unique index information for these views if they have a unique
combination of columns. You can then scroll backward and forward, but the MS SQL
Server data source does not allow you to create or delete data in a multi-table view.
You can, however, update data in some views.
The DataServer does not support access to columns in views that are the results of
aggregates or computations unless the calculated column has a name associated with
it. You assign a specific name to a calculated column when you define a data source
view. For example, the following SQL statement names a computed column in a view
definition:
create view view-name as select cc = count(cust_num) from customer
You can also access those views by using the RUN STORED–PROC send–sql–statement
option to send a SQL statement to select the data from the view. In this case, you can
access the view without adding index definitions for the view to the schema holder.
Although the schema holder contains your views, the Data Dictionary’s SQL View
Report does not list them, nor can you access them through the PRO/SQL menu
functions.
68 OpenEdge Data Management: DataServer for Microsoft SQL Server