Database Reference
In-Depth Information
You can also get a list of items older than or equal to the year 1999 by using the
$lte
(less than or equal to) parameter:
> db.media.find( {Released : {$lte: 1999}}, { "Cast" : 0 })
{ "_id" : ObjectId("4c43694bc603000000007ed1"), "Type" : "DVD", "Title" :
"Matrix, The", "Released" : 1999 }
{ "_id" : ObjectId("4c436969c603000000007ed2"), "Type" : "DVD", "Title" :
"Blade Runner", "Released" : 1982 }
You can also combine these parameters to specify a range:
> db.media.find( {Released : {$gte: 1990, $lt : 2010}}, { "Cast" : 0 })
{ "_id" : ObjectId("4c43694bc603000000007ed1"), "Type" : "DVD", "Title" :
"Matrix, The", "Released" : 1999 }
These parameters might strike you as relatively simple to use; however, you will be
using them a lot when querying for a specific range of data.
Retrieving All Documents but Those Specified
You can use the
$ne
(not equals) parameter to retrieve every document in your collection,
except for the ones that match certain criteria. For example, you can use this snippet to
obtain a list of all topics where the author is not Eelco Plugge:
> db.media.find( { Type : "Book", Author: {$ne : "Plugge, Eelco"}})
Specifying an Array of Matches
You can use the
$in
operator to specify an array of possible matches. The SQL equivalent
is the
IN
operator.
You can use the following snippet to retrieve data from the media collection using
the
$in
operator:
> db.media.find( {Released : {$in : [1999,2008,2009] } }, { "Cast" : 0 } )
{ "_id" : ObjectId("4c43694bc603000000007ed1"), "Type" : "DVD", "Title" :
"Matrix, The", "Released" : 1999 }
This example returns only one item, because only one item matches the release year
of 1999, and there are no matches for the years 2008 and 2009.
