# Collections

# Create a Collection

First Select Or Create a database.

> use mydb
switched to db mydb

Using db.createCollection("yourCollectionName") method you can explicitly create Collection.

> db.createCollection("newCollection1")
{ "ok" : 1 }

Using show collections command see all collections in the database.

> show collections
newCollection1
system.indexes
> 

The db.createCollection() method has the following parameters:

Parameter Type Description
name string The name of the collection to create.
options document Optional. Configuration options for creating a capped collection or for preallocating space in a new collection.

The fllowing example shows the syntax of createCollection() method with few important options

>db.createCollection("newCollection4", {capped :true, autoIndexId : true, size : 6142800, max : 10000})
{ "ok" : 1 }

Both the db.collection.insert() and the db.collection.createIndex() operations create their respective collection if they do not already exist.

> db.newCollection2.insert({name : "XXX"})
> db.newCollection3.createIndex({accountNo : 1})

Now, Show All the collections using show collections command

> show collections
newCollection1
newCollection2
newCollection3
newCollection4
system.indexes

If you want to see the inserted document, use the find() command.

> db.newCollection2.find()
{ "_id" : ObjectId("58f26876cabafaeb509e9c1f"), "name" : "XXX" }

# Drop Collection

MongoDB's db.collection.drop() is used to drop a collection from the database.

First, check the available collections into your database mydb.

> use mydb
switched to db mydb

> show collections
newCollection1
newCollection2
newCollection3
system.indexes

Now drop the collection with the name newCollection1.

> db.newCollection1.drop()
true

Note: If the collection droped successfully then the method will return true otherwise it will return false.

Again check the list of collections into database.

> show collections
newCollection2
newCollection3
system.indexes

Reference: MongoDB drop() Method.

# Remarks

Create Database