SQL Server: query for getting TOP X groups of records which have highest subsequent values
If you run this:

select dbname, AVG(usage), STDEV(usage) from &lt;your table&gt; group by dbname


You'll notice that while the average is the same for both databases, the one you'd be interested is the one where the standard deviation is lower.  So what you'd want to do is then filter this by a certain threshold average usage or higher and a certain standard deviation or lower.