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DBFILTER()
Return the current filter expression as a character string
------------------------------------------------------------------------------
Syntax
DBFILTER() --> cFilter
Returns
DBFILTER() returns the filter condition defined in the current work area
as a character string. If no FILTER has been SET, DBFILTER() returns a
null string ("").
Description
DBFILTER() is a database function used to save and re-execute an active
filter by returning the filter expression as a character string that can
be later recompiled and executed using the macro operator (&). This
function operates like the DBRELATION() and DBRSELECT() functions which
save and re-execute the linking expression of a relation within a work
area.
Since each work area can have an active filter, DBFILTER() can return
the filter expression of any work area. This is done by referring to
DBFILTER() within an aliased expression as demonstrated below.
Notes
. Declared variables: A character string returned by DBFILTER()
may not operate correctly when recompiled and executed using the
macro operator (&) if the original filter expression contained
references to local or static variables, or otherwise depended on
compile-time declarations.
Examples
. This example opens two database files, sets two filters, and
then displays the filter expressions for both work areas:
USE Customer INDEX Customer NEW
SET FILTER TO Last = "Smith"
USE Invoices INDEX Invoices NEW
SET FILTER TO CustId = "Smi001"
SELECT Customer
//
? DBFILTER() // Result: Last = "Smith"
? Invoices->(DBFILTER()) // Result: Custid = "Smi001"
. This user-defined function, CreateQry(), uses DBFILTER() to
create a memory file containing the current filter expression in the
private variable cFilter:
FUNCTION CreateQry( cQryName )
PRIVATE cFilter := DBFILTER()
SAVE ALL LIKE cFilter TO (cQryName + ".qwy")
RETURN NIL
. You can later RESTORE a query file with this user-defined
function, SetFilter():
FUNCTION SetFilter()
PARAMETER cQryName
RESTORE FROM &cQryName..qwy ADDITIVE
SET FILTER TO &cFilter.
RETURN NIL
Files Library is CLIPPER.LIB.
See Also:
DBRELATION()
DBRSELECT()
SET FILTER
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