INDEXKEY() Return the key expression of a specified index ------------------------------------------------------------------------------ Syntax INDEXKEY(<nOrder>) --> cKeyExp Arguments <nOrder> is the ordinal position of the index in the list of index files opened by the last USE...INDEX or SET INDEX TO command for the current work area. A zero value specifies the controlling index, without regard to its actual position in the list. Returns INDEXKEY() returns the key expression of the specified index as a character string. If there is no corresponding index or if no database file is open, INDEXKEY() returns a null string (""). Description INDEXKEY() is a database function that determines the key expression of a specified index in the current work area and returns it as a character string. To evaluate the key expression, specify INDEXKEY() as a macro expression like this: &(INDEXKEY(<nOrder>)). INDEXKEY() has a number of applications, but two specific instances are important. Using INDEXKEY(), you can TOTAL on the key expression of the controlling index without having to specify the key expression in the source code. The other instance occurs within a DBEDIT() user function. Here, you may want to determine whether or not to update the screen after the user has edited a record. Generally, it is only necessary to update the screen if the key expression of the controlling index has changed for the current record. Both of these examples are illustrated below. By default, INDEXKEY() operates on the currently selected work area. It can be made to operate on an unselected work area by specifying it within an aliased expression (see example below). Examples . This example accesses the key expression of open indexes in the current work area: #define ORD_NATURAL 0 #define ORD_NAME 1 #define ORD_SERIAL 2 // USE Customer INDEX Name, Serial NEW SET ORDER TO ORD_SERIAL ? INDEXKEY(ORD_NAME) // Result: Name index exp ? INDEXKEY(ORD_SERIAL) // Result: Serial index exp ? INDEXKEY(ORD_NATURAL) // Result: Serial index exp . This example accesses the key expression of the controlling index in an unselected work area: USE Customer INDEX Name, Serial NEW USE Sales INDEX Salesman NEW ? INDEXKEY(0), Customer->(INDEXKEY(0)) . This example uses INDEXKEY() as part of a TOTAL ON key expression. Notice that INDEXKEY() is specified using a macro expression to force evaluation of the expression: USE Sales INDEX Salesman NEW TOTAL ON &(INDEXKEY(0)) FIELDS SaleAmount TO ; SalesSummary . This example uses INDEXKEY() to determine whether the DBEDIT() screen should be updated after the user has edited the current field value. Generally, you must update the DBEDIT() screen if the user changes a field that is part of the controlling index key. FieldEdit() is a user-defined function called from a DBEDIT() user function to edit the current field if the user has pressed an edit key. #include "Dbedit.ch" #define ORD_NATURAL 0 FUNCTION FieldEdit() LOCAL indexVal // Save current key expression and value indexVal = &(INDEXKEY(ORD_NATURAL)) . . <code to GET current field value> . // Refresh screen if key value has changed IF indexVal != &(INDEXKEY(ORD_NATURAL)) nRequest = DE_REFRESH ELSE nRequest = DE_CONT ENDIF RETURN nRequest Files Library is CLIPPER.LIB.
See Also: INDEX INDEXEXT() INDEXORD() SET INDEX SET ORDER