query1.sql.add('select * from table where field1 between :firstvalue and :secondvalue');
query1.parambyname('firstvalue').value:=strtoint(edit1.text);
query1.parambyname('secondvalue').value:=strtoint(edit2.text);
query1.open;
var
strsql : string;
begin
strsql := 'select * from country where
(area <'+edit1.text+') and (area >'+edit2.text')'
end;
query1.close;
query1.sql.clear;
query1.sql.add(strsql);
query1.open;
人口类似
