The database can be search like so:

Reports
-> by Date
-> by Command Filename (eg. "nmap_fast_scan.cmd")
-> by Target ip/ip-range (eg "192.168.0.1 OR 192.168.0.0/100"
-> by Report ID (a unique hash for every processed report)
-> by Length of Scan Time (eg "length > 2 hours")
-> by Scanning Application Name (eg "Nmap 1.2")

Hosts
-> By Date Added
-> By Date Last Seen
-> By IP
-> By Hostname
-> By Ports Open
-> By Services Enabled 
-> By City
-> By Country
-> By Metadata Token (any string tokens contained in responses)
-> By NetRange (eg "between 192.168.0.1 and 192.168.0.100")