Progress
DataServer for
Microsoft SQL Server
Guide
Defining a View to Use As a Buffer
If you do not use the buffer proc–text–buffer defined by Progress, you must define your own. Defining a view in the data source that can serve as a buffer allows you to retrieve database results in their original data types.
While a stored procedure can include multiple SQL statements, a buffer that you define holds the results of only a single SQL statement.
Follow these steps to define a buffer:
- Define a view in the MSS data source:
- With the naming convention _BUFFER_buffername
- With the same number of columns and data types that the stored procedure returns in the results set
- With the columns in the order that the stored procedure returns them
For example, to return two columns with two types of values, an integer and a character string, use an SQL utility to define the following view in the data source:
Notice that these views are defined to ensure that they never return any results. This indicates that you will not use the views as views, but as buffers. It is not necessary to define views that you will use as buffers this way, but it does allow you to distinguish quickly between views and buffers.
- Update your schema image using the Update/Add Table Definitions DataServer utility. The utility adds the view to the list of accessible objects in the schema holder. The DataServer defines the view as a buffer that Progress can use.
See the "Updating a Schema Holder" section in "The DataServer Tutorial," for instructions on using this utility.
This buffer defines two returned values for a stored procedure—an INTEGER and a CHARACTER value—in that order. If the data types do not match those returned by the stored procedure, the procedure returns more than two types of values, or returns the values in a different order than you specified, you receive a run-time error.
The easiest way to create a buffer that accepts data from stored procedures is to use the text of the SQL SELECT statement from the stored procedure. This ensures that you define your data types correctly and in the correct order. Use a native process such as sp_helptext to view the stored procedure from SQL Server™, or view procedures in the system tables.
The next example does not use the supplied buffer. Instead, it defines buffers by creating views in the data source, using the following syntax:
The following examples are of the views created in your MSS data source that you can use as buffers to store the results from the stored procedure pcust:
The following 4GL procedure shows the results of the stored procedure pcust being written into the new buffers pcust_orders and pcust_states:
Because two different buffers have been defined, the returned values maintain their data types instead of being converted to character strings and stored in the Progress-defined buffer proc–text–buffer. You can then use the returned values in calculations without first converting them back to their original data types. In addition, the two separate buffers make your output look cleaner, allowing Progress to build a new default frame for the two different types of output. Reading your results into an explicitly defined buffer also allows you to manipulate the data just as you would manipulate data from a Progress database; for example, with Frame phrases and FORM statements.
The next example accesses the stored procedure pcust twice; procedure handles (through the PROC–HANDLE function) identify the different results from your data source:
In this example, the results look the same as in the previous example. However, because you are running a stored procedure twice, Progress uses the procedure handles to identify the different instances. If you run more than one stored procedure in your application, you must explicitly define procedure handles for each.
The next example shows how to use standard Progress syntax to join the results of the stored procedures with other tables in the database:
This example joins the order information returned from the stored procedure with the order–line information in the same database.
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