How to compare a "grand total" sum() to a group by sum?

I've got a testing table containing names and misc numbers. What i'm trying to do is;

1. get the sum of column_1 for each name within a date range
2. get the sum of column_2 for each name within a date range
3. get the percentage amount of column_1 against column_2 for each name within a date range.

and finally
4. get the total sum of column_1 for ALL names within a date range to calculate a percentage of column_1 for each name.

1-3 have been accomplished using 'Group By'. The problem I have now is, How do I include part 4, getting the grand total sum of all rows and not have it affected by 'Group By'? I've had no luck so far.

The working query for parts 1-3 is:

[MYSQL]
SELECT name,
SUM(column_1) as 'Attempt',
SUM(column_2) as 'Success',
(SUM(column_2) * 100) / SUM(column_1) as 'Percent_of_own'
FROM activelog WHERE column_1 > 0 AND
entrydate BETWEEN '2012/01/01' AND '2013/01/01'
GROUP BY name;
[/MYSQL]

This works fine. But now I want to somehow include something like:
(SUM(column_1) * 100) / << Grand Total>> AS 'Percent_of_all"

A sample or pointer to online resources, examples would be appreciated!

@r937
Brilliant! Thank you. Your example is super clean and easy to follow. I came close in one of my attempts, but had one of the parens in the wrong place - Select(SUM... instead of (SELECT SUM ...

Thanks again for your help!