Database Reference
In-Depth Information
u'Owner': u'Martin, Lisa',
u'DeskNumber': 131151
}
}
Note that the
$inc
operator works only on integer values (that is, numeric values), but not on any string values or
even numeric values added as a string (for example,
"123"
vs.
123
).
Changing an Existing Value with $set
You use the
$set
operator to change an existing value in any matching document. This is an operator you'll use
frequently. The next example changes the value from
"Building"
in any item currently matching the key/value
"Location.Department / Development"
.
First use
$set
to perform the update, ensuring that all documents are updated:
>>> collection.update({"Location.Department" : "Development"},
... {"$set" : {"Location.Building" : "3B"} },
... multi = True )
Next, use the
find_one()
command to confirm that all went well:
>>> collection.find_one({"Location.Department" : "Development"}, fields={"Location.Building" :
True})
{
u'_id': ObjectId('4c57207b4abffe0e0c000000'),
u'Location': {u'Building': u'3B'}
}
Removing a Key/Value Field with $unset
Likewise, you use the
$unset
operator to remove a key/value field from a document, as shown in the following
example:
>>> collection.update({"Status" : "Not used", "ItemNumber" : "2345FDX"},
... {"$unset" : {"Location.Building" : 1 } } )
Next, use the
find_one()
command to confirm all went well:
>>> collection.find_one({"Status" : "Not used", "ItemNumber" : "2345FDX"}, fields={"Location" :
True})
{
u'_id': ObjectId('4c592eb84abffe0e0c000004'),
u'Location': {u'Department': u'Storage'}
}
