OpenEdge Data Management: DataServer for Microsoft SQL Server

Join by SQLDB
FOR EACH customer, EACH order
WHERE customer.custnum = order.custnum AND customer.custnum GT 100:
However, for the following query, the DataServer instructs the client to perform the join
because of the OR option:
FOR EACH customer, EACH order
WHERE customer.custnum = order.custnum OR customer.custnum GT 100:
By default, the DataServer instructs a MS SQL Server data source to perform a join when
possible and when desirable. However, you can control the default behavior by using either the
QUERY–TUNING NO–JOIN–BY–SQLDB phrase or the Server Join (-nojoinbysqldb) startup
parameter. The QUERY–TUNING phrase controls the behavior for a single query. The
-nojoinbysqldb parameter controls it at the session level. The query-level setting overrides the
session-level setting.
Table 4–2 describes how these controls interact and affect the behavior.
Table 4–2: Controlling join by SQLDB behavior
QUERY–TUNING Startup Parameter Behavior
JOIN–BY–SQLDB -nojoinbysqldb The MS SQL Server data source
performs the join if possible.
JOIN–BY–SQLDB None The MS SQL Server data source
performs the join if possible.
NO–JOIN–BY–SQLDB -nojoinbysqldb The client performs the join.
NO–JOIN–BY–SQLDB None The client performs the join.
None -nojoinbysqldb The client performs the join.
None None The MS SQL Server data source
performs the join if possible and the
join contains the selection criteria
described previously.
A join by SQLDB does not occur by default for the following query because the DataServer
determines that it does not increase performance:
FOR EACH customer, EACH order:
You receive a warning if you specify JOIN–BY–SQLDB when the MS SQL Server data source
cannot perform the join and the DataServer performs the join instead. You receive a warning at
compile time if you specify JOIN–BY–SQLDB when the data source can perform the join but it is
not optimal for it to do so.
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