with datamodule4.ADOcommand1 do
                 begin
                    close;
                    s:='insert into orders(orderid,productid,customername.number,orderdate,completedate,shenghe,jiaohuo) ';
                    s:=s+ 'values(edit1.text,copy(combobox1.text,1,pos('-',combobox1.text)),edit2.text,edit3.text,dbdatetimeediteh1.value,dbdatetimeediteh2.value,0,0)';
                    commandtext:=s;
                    execute;
                     showmessage('保存成功！');
                  end;
        end;

[DCC Error] Unit6.pas(145): E2015 Operator not applicable to this operand type
s:='insert into orders(orderid,productid,customername.number,orderdate,completedate,shenghe,jiaohuo) ';
s:=s+ 'values('''+edit1.text,copy(combobox1.text,1,pos('-',combobox1.text))+''','''+edit2.text+''','''+edit3.text+','''+datetostr(dbdatetimeediteh1.value)+''','''+datetostr(dbdatetimeediteh2.value)+''',0,0)';

单引号内都会被认定为字符串，比如你的edit1.text 只会显示字符串而不是里面的数据，你可以加断点跟踪下commandtext的值；一楼写法比较正确。