filter( ) 函数示例

close databases
open database (home(2) + 'data\testdata')
use customer  && opens customer table
set talk on
set filter to substr(cust_id,1) = 'b'
clear
? filter( )  && display filter expression
store filter('customer') to gcoldfilter    && save filter expression
set filter to country = 'usa'
? filter( )  && display filter expression
set filter to &gcoldfilter    && restore filter expression
? filter( )  && display filter expression
list fields cust_id, contact  && demonstrate filter condition