数据库是paradox,求c41(N型)字段的最大值
procedure Ttj4.Button1Click(Sender: TObject);
var
xy:double;
begin
dm.Qjhb.close;
dm.qjhb.SQL.clear;
dm.qjhb.sql.add('select max(c41) as c441 from jhb');
dm.qjhb.open;
xy:=dm.qjhb.fieldbyname('c441').asfloat;;
showmessage(floattostr(xy));
end;
procedure Ttj4.Button1Click(Sender: TObject);
var
xy:double;
begin
dm.Qjhb.close;
dm.qjhb.SQL.clear;
dm.qjhb.sql.add('select max(c41) as c441 from jhb');
dm.qjhb.open;
xy:=dm.qjhb.fieldbyname('c441').asfloat;;
showmessage(floattostr(xy));
end;
procedure Ttj4.Button1Click(Sender: TObject);
var
xy:double;
begin
dm.Qjhb.close;
dm.qjhb.SQL.clear;
dm.qjhb.sql.add('select max(c41) from jhb');
dm.qjhb.open;
xy:=dm.qjhb.fields[0].asfloat;;
showmessage(floattostr(xy));
end;