The foloowing codes demonstrate the creation (C), query (R), update (U) and delete (D) operations on mongodb collections.
It also shows how to rename collections and keys of documents.
$ mongo
db.fairs.insert({'name': 'bikeShow', 'time': '2014.12.24', 'location': 'Beijing', 'products': ['bike', 'car', 'truck']})
db.fairs.insert({'name': 'clothShow', 'time': '2014.2.14', 'location': 'Shanghai', 'products': ['silk', 'wood', 'paper']})
db.fairs.insert({'name': 'MyFruits', 'time': '2011.4.18', 'location': 'Guangzhou', 'products': ['berry', 'apple', 'banana']})
db.newfairs.find({}, {name: 1})
db.newfairs.find({}, {'name.chn': 1})
db.fairs.renameCollection('newfairs')
db.newfairs.update({}, {$rename: {'time': 'date'} }, {multi: true} )
db.newfairs.update({}, {$rename: {'name': 'names'} }, {multi: true} )
db.newfairs.update({}, {$rename: {'names': 'name.chn'} }, {multi: true} )
db.newfairs.update({}, {$unset: {'date': ""}}, {multi: true})
db.newfairs.remove({})
db.newfairs.drop()
exit
You can't use {$rename: {'name': 'name.chn'}} directly for "$rename must not be on the same path".
-
Find docs whose "website" field is not null:
db.fairs.findOne({$where: "this.website.length > 0" } ); -
Remove all docs whose "position" field is an empty string:
db.fairs.remove( { $where: "this.position.length == 0" } );