Query document in MongoDB 2016-05-29 06:38
In MongoDB db.collection.find() method query documents from the collection. If there is no param in it or passing empty param like this db.collection.find({}) will get all documents in this collection. It is like using select * from table_name in structural database.
> db.user.find()
{ "_id" : ObjectId("5747b01d4bca08a38db22ad3"), "name" : "Henry" }
{ "_id" : ObjectId("5747b1562a9f793542c63acc"), "name" : "Xi" }
{ "_id" : ObjectId("5747b1562a9f793542c63acd"), "name" : "Justin", "age" : 27 }
{ "_id" : ObjectId("5747b8a12a9f793542c63ace"), "name" : "Mathew", "age" : 23, "address" : { "country" : "China", "province" : "Beijing" } }
If you want to query the document which name is "Xi". You can use the query document {name:"Xi"} or {"name","Xi"}.
> db.user.find({name:"Xi"})
{ "_id" : ObjectId("5747b1562a9f793542c63acc"), "name" : "Xi" }
> db.user.find({"name":"Xi"})
{ "_id" : ObjectId("5747b1562a9f793542c63acc"), "name" : "Xi" }
Query the document which name exist in the array. Following query find the document which name in ["Xi","Mathew"]
> db.user.find({"name":{$in:["Xi","Mathew"]}})
{ "_id" : ObjectId("5747b1562a9f793542c63acc"), "name" : "Xi" }
{ "_id" : ObjectId("5747b8a12a9f793542c63ace"), "name" : "Mathew", "age" : 23, "address" : { "country" : "China", "province" : "Beijing" } }
Query the document with AND conditions. If there is no document match the condition MongoDB will return empty. You can use db.collection.count() method to count the number of documents.
> db.user.find({name:"Justin",age:27})
{ "_id" : ObjectId("5747b1562a9f793542c63acd"), "name" : "Justin", "age" : 27 }
> db.user.find({name:"Justin",age:23})
> db.user.count({name:"Justin",age:23})
0
Query the document with OR conditions.
> db.user.find({$or:[{name:"Henry"},{age:27}]})
{ "_id" : ObjectId("5747b01d4bca08a38db22ad3"), "name" : "Henry" }
{ "_id" : ObjectId("5747b1562a9f793542c63acd"), "name" : "Justin", "age" : 27 }
For embedded document we can query like following. Do not lose dot in "address.country"
> db.user.find({"address.country":"China"})
{ "_id" : ObjectId("5747b8a12a9f793542c63ace"), "name" : "Mathew", "age" : 23, "address" : { "country" : "China", "province" : "Beijing" } }
> db.user.find({"address.province":"Beijing"})
{ "_id" : ObjectId("5747b8a12a9f793542c63ace"), "name" : "Mathew", "age" : 23, "address" : { "country" : "China", "province" : "Beijing" } }
The result of query is not formatted. Format query result in MongoDB