OpenEdge Data Management: DataServer for Microsoft SQL Server

Additional Features to Enhance DataServer Performance
OpenEdge query types
4–8
The DataServer provides several ways to submit an OpenEdge query to a MS SQL Server data
source:
• ABL — This approach applies to the DEFINE QUERY and FOR EACH statements. The
DataServer generates SQL for each of these statements. You can use the QUERY–TUNING
option to customize the queries that the DataServer passes to ODBC.
• OpenEdge SQL SELECT — This approach applies to the SQL SELECT statement. When
you use this statement in an OpenEdge procedure, the DataServer passes the SQL directly
to the data source. This can improve performance, especially when counting records, and
can also allow you to access certain types of data more effectively, such as aggregates.
• Vendor-specific SQL — This approach applies to RDBMS stored procedures. If you
want to use specialized query syntax supported only by Transact-SQL extensions, you can
use RUN–STORED–PROC send–sql–statement to send the syntax to MS SQL Server. You
might use a stored procedure to include BEGINS as a search criterion; this SQL query can
result in better performance. For more information, see Chapter 3, “RDBMS Stored
Procedure Details.”
Whether your application can take advantage of the strengths of a particular approach depends
on the kind of query you are writing and the kind of data you are accessing. Another factor to
keep in mind when you decide which technique to use for issuing queries is whether a query is
better served by being processed by the client or by the server. ABL queries are processed by
the client (except in the cases of most joins); SQL SELECT statements and Transact-SQL
extensions are processed by the server.