Re: Count group errcode 28 - No space left on device

[Phillip Ward]

And not just the original 38 million records, either!
By using the "( select ... )" syntax, MySQL is having to create a temporary, in -memory 'table' containing all the data you select within that 'sub-select' (wrong word, I know, but you get the idea). That's almost certainly filling the server's working memory and spilling over onto disk, hence the 'disk full' message.
If I read this aright, these pseudo tables are used to generate the counts that you're including with the raw data - is there no way that you can calculate these within your application layer?