what am i doing wrong controlling rand() ms sql server 2005?

i'm perplexing name futile 10% sampling little table. i guess i'd only rand() duty name those rows where futile array reduction 0.10:

select * sometable
where somecolumn='somecondition' and
      rand() < 0.10

but i shortly detected rand() always advantage same number! reminds me .

ok, problem, rand duty takes seed value. i controlling query periodically, i wish give opposite law i run opposite day, i seed multiple date unparalleled quarrel id:

select * sometable
where somecolumn='somecondition' and
      rand(cast(getdate) integer) + rowid) < 0.10

i still don't any results! i arrangement futile numbers returned rand, i learn they're within slight range. appears removing futile array rand requires futile seed. i futile seed initial place, i wouldn't need futile number!

i've seen before discussions associated problem:

they don't assistance me. tablesample works during page level, good large list nonetheless little one, looks relates before where clause. tip newid doesn't work since i don't know disrespectful rows i want.

anybody have solution, during slightest hint?

edit: interjection alexcuse works sole case. incomparable question, rand behave?