You can enable more powerful views using the custom query language.

The basic format is:

<field> <comparison> [value] [<logic operator> <field> <comparison> [value] [...]]

Field names:
	TYPE: 0 for audio files, 1 for video files
	FILENAME: Full filename (including path)
	LENGTH: Length, in seconds (or hh:mm:ss)
	ARTIST: Artist
	ALBUM: Album
	ALBUMARTIST: Album Artist
	TITLE: Title
	TRACKNO: Track number of file
	GENRE: Genre
	YEAR: Year
	COMMENT: Comment
	COMPOSER: Composer
	DISC: Disc number of a CD set
	FILESIZE: File size, in kilobytes
	FILETIME: Last known file date/time on disk
	LASTUPD: Date/time of file imported to library or modified in library
	LASTPLAY: Date/time of last play
	RATING: Rating value (1-5, or 0 or empty for unrated)
	PLAYCOUNT: Number of plays
	PUBLISHER: Publisher or record label
	DIRECTOR: Film director (for videos)
	PRODUCER: Film or Record producer
	CATEGORY: Category
	REPLAYGAIN_ALBUM_GAIN: ReplayGain Album Gain
	REPLAYGAIN_TRACK_GAIN: ReplayGain Track Gain
	BITRATE: Bitrate (in KBPS)
	TRACKS: Total number of tracks on the disc
	DISCS: Total number of discs in the set
	ISPODCAST: 1 for a podcast episode, 0 otherwise
	PODCASTCHANNEL: The name of the channel for a podcast
	PODCASTPUBDATE: Date/time when the podcast was published
	LOSSLESS: Shows lossless audio formats, e.g. lossless=1

Comparison operators:
	'=': String or integer equals value
	'!=': String or integer does not equal value
	'<': String or integer is less than value
	'>': String or integer is greater than value
	'<=': String or integer is less than or equal to value
	'>=': String or integer is greater than or equal to value
	HAS: String contains value
	NOTHAS: String does not contain value
	LIKE: String is similar to value ("the" and whitespace are ignored)
	BEGINS: String begins with value
	BEGINSLIKE: String begins like value
	ENDS: String ends with value
	ISEMPTY: (no comparison value required) TRUE if <field> is empty
	ISNOTEMPTY: (no comparison value required) TRUE if <field> is not empty

Values:
	"strings with spaces" or strings_without_spaces
	integers can be "32" or just 32
	integers for LENGTH can be a plain integer (seconds), or mm:ss or hh:mm:ss
	date/timestamps should be [datetime data], which can be either an absolute
	  or relative time. i.e.: [3 weeks ago], [18:15],  [05/30/2003],
	  [yesterday noon], [3 days ago 5 pm], [now], [5 mn before may 30th], etc.

Logic operators:
	&&, &, or AND: boolean AND two comparisons
	||, |, or OR: boolean OR two comparisons
	!, or NOT: prefix this to an expression for the boolean NOT of that expression

Examples:
  all video files: type = 1
  audio by Air longer than 4 minutes: type = 0 & artist = "air" & length > 4:00
  all files on drive C: filename BEGINS C:
  high rated items that haven't been played lately: rating > 3 & lastplay < [1 week ago]
  newly added items that haven't been played yet: lastupd >= [yesterday] & playcount <= 0

Note that you can also use this syntax in the search field of views. Simply prefix a '?' or 'query:' to your search string