SELECT
Change the current work area
Syntax
SELECT <xnWorkArea> | <idAlias>
Arguments
<xnWorkArea> is the work area number between 0 and 250 inclusive. This argument is an extended expression and can be specified either as a literal number or as a numeric expression enclosed in parentheses.
<idAlias> is the name of an existing work area to SELECT if there is a database file open in that area.
Description
SELECT is a database command that changes work areas. CA-Clipper supports 250 work areas, with each work area a logical handle to an open database file and all of its attributes. You can refer to work areas with SELECT by number or by alias. The alias of a work area is automatically assigned when a database file is USEd in that work area or by using the ALIAS clause.
Work area 0 refers to the first empty or next available work area. Using this, you can SELECT 0 and USE <xcDatabase> as a method of opening database files.
Notes
. Aliased expressions: Aliased expressions are a much more powerful method of selecting new work areas than the SELECT command. Instead of SELECTing a work area, and then performing an operation for that work area, you can apply an alias to an expression that performs the operation. This is done by specifying the alias of the remote work area and the expression enclosed in parentheses. For example, to access the value of EOF() in an unselected work area, you would normally execute a series of statements like the following:
SELECT Remote
? EOF()
SELECT Main
Using the aliased expression form, these statements become:
? Remote->(EOF())
. USE…NEW: Instead of using SELECT0 and USE <xcDatabase> to open a database file in a new work area, the preferred method is to USE <xcDatabase> NEW.
Examples
. This example opens a series of database files by SELECTing
each work area by number then USEing each database file in that
work area:
SELECT 1
USE Customer
SELECT 2
USE Invoices
SELECT 3
USE Parts
SELECT Customer
. A better method is to open each database in the next available
work area by specifying the NEW clause on the USE command line.
In this example USE...NEW is employed instead of SELECT 0 and
then USE:
USE Customer NEW
USE Invoices NEW
SELECT Customer
. This code fragment changes work areas while saving the current
work area name to a variable using the SELECT() function. After
executing an operation for the new work area, the original work
area is restored:
nLastArea := SELECT()
USE Newfile NEW
//
<statements>...
//
SELECT (nLastArea)
Seealso
ALIAS(), EOF(), SELECT(), SET INDEX, USE, USED()
Viva Clipper ! 