UPDATE t SET nal_sz = 1 
FROM t
WHERE dbo.AccountCount(kod_pr, dat)= 0


CREATE FUNCTION [dbo].[AccountCount]
(@kod_pr int, @dat datetime)
RETURNS int
AS
BEGIN
	declare @count int
	
	set @count = (select count(distinct dat) 
	from t where dat<@dat and kod_pr=@kod_pr)
	
	return @count

END

UPDATE t SET nal_sz = (select Count(distinct ff.dat) + 1 
from t f
where f.kod_pr=t.kod_pr and f.dat<t.dat)
FROM t