SQL和C++Builder6的问题

strSQL="Select UserName from ReaderTable where UserName='"+
LoginForm->UserEdit->Text+"'";
strPass="Select Password from ReaderTable where Password='"+LoginForm->PassEdit->Text +"'";
if(strSQL==""||strPass=="")
{ ShowMessage("非法");
}
为什么显示不出非法??那怎样才能验证有该用户或没该用户?
应该怎样改???谁能说一下?

strSQL与strPass只是两个String型的变量.
而你在前面已经赋值了,if(strSQL==""||strPass=="")自然不会成立..
你必须要执行这两条语句,得到返回记录..用返回的记录来判断才行...

以下是我写的:(判断用户登录成功)
if(UserEdit->Text == "" || PassEdit->Text == "")
{
MessageBox(Handle,"用户名或密码不能为空","提示",MB_OK|MB_ICONINFORMATION);
return;
}
sp_Statics->Active = false; //Statics是SP控件
//sp_Statics->Parameters->Items[0]->Value
sp_Statics->Parameters->ParamByName("@username")->Value = UserEdit->Text;
sp_Statics->Parameters->ParamByName("@password")->Value = PassEdit->Text;
sp_Statics->Active = true;
if(sp_Statics->RecordCount<=0)
{
MessageBox(Handle,"用户名或密码错误","提示",MB_OK|MB_ICONINFORMATION);
edtUserName->SetFocus();
return;

}