Question

I have something like this:

 Name.....Value
 A...........10 
 B............9
 C............8

Meaning, the values are in descending order. I need to create a new table that will contain the values that make up 60% of the total values. So, this could be a pseudocode:

set Total = sum(value) 
set counter = 0 
foreach line from table OriginalTable do: 
counter = counter + value 
if counter > 0.6*Total then break
else insert line into FinalTable
end

As you can see, I’m parsing the sql lines here. I know this can be done using handlers, but I can’t get it to work. So, any solution using handlers or something else creative will be great.
It should also be in a reasonable time complexity – the solution how to select values that sum up to 60% of the total
works, but it’s slow as hell 🙁
Thanks!!!!

Answer 1

You’ll likely need to use the lead() or lag() window function, possibly with a recursive query to merge the rows together. See this related question:

merge DATE-rows if episodes are in direct succession or overlapping

And in case you’re using MySQL, you can work around the lack of window functions by using something like this:

Mysql query problem