Help! I got a 5 out of memory error.

Hello.
My website(e.g.https://www.xxx.com) appears a error yesterday at about 16:00 and the site could not be visited.
The error appears like this:

5 Out of memory (Needed 1677676 bytes)
in:
[select c.categories_id,cd.categries_name,c.parent_di,c.categories_description cd where
c.parent_id=0 and
c.categories_id=
cd.categories_id and
cd.language_id='1' and
c.categories_status=1 order by
sort_order,cd.categories_name]

I used the command "tracert https://www.xxx.com" ping https://www.xxx.com ping db.xxx.com and it's OK to complete the tracert.
I searched this error on Google but there is few infomation about this . One of there explanation is :"" the host memory limit is too low(16M) and it can be configured by the website host.""
And i'm not really sure this will solve the problem because someone else said: 'there site host memory is 100M+,and that error appears,too...'
If anyone have experiences to solve this problem ,please tell me what to do .And i'm looking for any reply . Thanks.

Wolf In