if not exists(select null from t1 where date1=@date1 and date2=@date2 and p1 = @p1 and p2 = @p2 and ...)
begin
    delete from t1 where date2<@date2
    
    insert into t1
        select
         @date1 date1
        ,@date2 date2
        ,@p1    p1
        ,@p2    p2
        ,...
        from
        ...
end
else
    select ... from t1