adotable怎么查找下一条记录delphi

begin
with Data_M.ADO_user do
begin
if trim(Fieldbyname('username').Value) = edit1.Text then
begin
if trim(Fieldbyname('password').Value) = edit2.Text then
begin
next;
main_form.Show;
login_form.Visible := false;
end else
begin
showmessage('您输入的密码错误');
edit1.SetFocus;
end;
end else
begin
showmessage('您输入的账号有误');
edit2.SetFocus;
end;
end;
end;

表中有两条记录
username password
1.admin admin
2.jeff 123
我这样子写只能找到第一条admin的记录 而jeff这条记录一直找不到
哪里错了呢
如果使用过滤器
filter :='name = ''' + edit1.Text + '''' ;
filtered := true;
怎么添加修改代码???

begin
with Data_M.ADO_user do
begin

close;

sql.clear;

sql.add('select * from 表 where username='''+edit1.text+''' ');

open;
if RecordCount>0 then
begin
if trim(Fieldbyname('password').Value) = edit2.Text then
begin
main_form.Show;
login_form.Visible := false;
end else
begin
showmessage('您输入的密码错误');
edit1.SetFocus;
end;
end else
begin
showmessage('您输入的账号有误');
edit2.SetFocus;
end;
end;
end;