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DBRSELECT()
Return the target work area number of a relation
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Syntax
DBRSELECT(<nRelation>) --> nWorkArea
Arguments
<nRelation> is the position of the desired relation in the list of
current work area relations. The relations are numbered according to
the order in which they were defined with SET RELATION.
Returns
DBRSELECT() returns the work area number of the relation specified by
<nRelation> as an integer numeric value. If there is no RELATION SET
for <nRelation>, DBRSELECT() returns zero.
Description
DBRSELECT() is a database function used in combination with DBRELATION()
to determine the work area and linking expression of an existing
relation created with the SET RELATION command. DBRSELECT() returns the
work area defined by the INTO clause. DBRELATION() returns the linking
expression defined by the TO clause. To determine the alias of the
relation instead of the work area number, use the expression
ALIAS(DBRSELECT(<nRelation>)).
By default, DBRSELECT() operates on the currently selected work area.
It will operate on an unselected work area if you specify it as part of
an aliased expression (see example below).
Examples
. This example opens three database files, sets two child
relations from the parent work area, and then displays the linking
expression to the second child work area, as well as the target work
area of the relation:
USE Invoices INDEX Invoices NEW
USE BackOrder INDEX BackOrder NEW
USE Customer INDEX Customer NEW
SET RELATION TO CustNum INTO Customer, ;
OrderNum INTO BackOrder
//
? DBRELATION(2), DBRSELECT(2) // Result: OrderNum 3
? ALIAS(DBRSELECT(2)) // Result: BACKORDER
. Later, you can query the same information from an unselected
work area by using an aliased expression:
USE Archive NEW
? Customer->(DBRELATION(2)) // Result: OrderNum
? Customer->(DBRSELECT(2)) // Result: 3
Files Library is CLIPPER.LIB.
See Also:
DBFILTER()
DBRELATION()
RLOCK()
UNLOCK
SET RELATION
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