4

In the MongoDB shell, how to views all documents in a particular collection for the current database that I'm using?

when i am trying through the query

> db.getCollection().find()

To getting the error as mention below

2017-10-14T00:57:34.363+0530 E QUERY    [thread1] Error: collection constructor called with undefined argument :
DB.prototype.getCollection@src/mongo/shell/db.js:34:16
@(shell):1:1

I am also uploading the screen shot of mongo shell command prompt here

enter image description here

5

OK, let's start from basics!

After you have connected to mongod with command mongo.

  • List databases with command show dbs

iot:PRIMARY> show dbs admin 0.000GB iot 0.020GB local 0.042GB test 0.000GB testi 0.000GB

  • Select one of the DB's with use iot command

iot:PRIMARY> use iot

switched to db iot

  • List collections on that DB with show collections command

iot:PRIMARY> show collections data header key

  • Make query to one of those collections

iot:PRIMARY> db.header.find() { "_id" : "1b5caa", "temp1" : "Temperature", "pressure1" : "Pressure", "humidity1" : "Humidity", "uv1" : "UV", "BusV1" : "Solar Panel (V)", "Current1" : "Solar Panel Current (mA)", "BusV2" : "Battery (V)", "Current2" : "Battery Current (mA)" } { "_id" : "30444", "temp1" : "Temperature", "pressure1" : "Pressure", "humidity1" : "Humidity" } { "_id" : "239684", "temp1" : "Temperature", "pressure1" : "Pressure", "humidity1" : "Humidity" }

So, you need to be connected WANTED database with use command and you need to show the one collection what you want to query with db.<collection_name>.find()

How to see to what database I'm connected currently? Just give command db and you get the answer what is your current DB.

  • Yes JJussi through db.<collection_name>.find(), i am able to find out all documents in a particular collection. Even db.getCollection('Document Name').find({}), also able to get the complete documents in a particular collection. so, i am going to a accept as a answer. – Md Haidar Ali Khan Oct 17 '17 at 5:19
  • Very good explanation for a beginner <3 – Menuka Ishan Dec 21 '18 at 10:46
2

Ref:

https://docs.mongodb.com/manual/tutorial/query-documents/

Select All Documents in a Collection

To select all documents in the collection, pass an empty document as the query filter parameter to the find method. The query filter parameter determines the select criteria:

db.inventory.find( {} )

These operation corresponds to the following SQL statement:

SELECT * FROM inventory
  • unable to find out through your query db.inventory.find( {} ). Even i have gone through the mention ref mongo documents, but not find out the exact my query desire.thanks – Md Haidar Ali Khan Oct 13 '17 at 19:53
  • Your query is wrong. it is dbname.collectionName.find( {} ) . Why are you using getcollection()? – SqlWorldWide Oct 13 '17 at 19:55
  • ,ok. Why are you using getcollection()? What do you mean by that? in respect of mongo shell query or else – Md Haidar Ali Khan Oct 13 '17 at 19:58
  • To find all documents in a collection the command is dbname.collectionname.find( {} ) – SqlWorldWide Oct 13 '17 at 20:00
  • As per your instruction when i am running the query like dbname.collectionname.find( {} ) then getting the error such as 2017-10-14T01:26:59.230+0530 E QUERY [thread1] ReferenceError: collectionname is not defined : @(shell):1:1 – Md Haidar Ali Khan Oct 13 '17 at 20:03

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