User Tools

Site Tools

Navigation:  ABC Library Reference > FileManager > FileManager Methods >====== ClearKey (clear specified key components) C6H0009.jpg ====== Previous pageReturn to chapter overviewNext page

ClearKey ( key [, firstcomponent] [, lastcomponent] [, highvalue] )


ClearKey Clears or (re)initializes the specified range of key component fields.
key The label of the KEY.
firstcomponent A numeric constant, variable, EQUATE, or expression that indicates the first component to clear. If omitted, firstcomponent defaults to one (1).
lastcomponent A numeric constant, variable, EQUATE, or expression that indicates the last component to clear. If omitted, lastcomponent defaults to twenty-two (22).
highvalue An integer constant, variable, EQUATE, or expression that indicates whether to clear the components to zero (or spaces for string fields) or to their highest possible values. A value of one (1) applies the highest possible value; a value of zero (0) applies spaces for strings and zeros for numerics. If omitted, highvalue defaults to zero (0).

The ClearKey method clears or (re)initializes the specified range of key component fields.

Implementation: ClearKey is useful for range limiting to the first instance of the first “free” key component. By retaining higher order key component values and clearing lower order key component values, you can fetch the first (or last) record that matches the retained higher order component values; for example, the first order (lower order key component) for a customer (higher order key component).

The value ClearKey assigns depends on three things: the data type of the component field (numeric or string), the sort direction of the component (ascending or descending), and the value of the highvalue parameter (True or False). The following table shows the values ClearKey assigns for each combination of data type, sort direction, and highvalue.

Numeric Fields String Fields
highvalue Ascending Descending Ascending Descending
True (1) High Values zero High Values Spaces
False (0) zero High Values spaces High Values


INCLUDE('ABFILE.INC')              !declare FileManager class
MAP                                !program map
GlobalErrors ErrorClass             !declare GlobalErrors object
Access:Order CLASS(FileManager)     !derive Access:Order object
IDKey     KEY(Ord:Cust,Ord:ID,Ord:Date),NOCASE,OPT,PRIMARY
Record    RECORD,PRE()
Cust       LONG
ID         LONG
Date       LONG
!program code
!find first order for current customer by clearing all components except Ord:Cust
Access:Order.ClearKey( ORD:IDKey, 2 )     !clear Ord:ID and Ord:Date
Access:Order.Fetch()                      !get the next record by key
clearkey_clear_specified_key_components_.htm.txt · Last modified: 2021/06/16 03:44 by carlbarnes