MongoDB - Create Collection

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In this chapter, we will see how to create a collection using MongoDB.

The createCollection() Method

MongoDB db.createCollection(name, options) is used to create collection.

Syntax

Basic syntax of createCollection() command is as follows −

db.createCollection(name, options)

In the command, name is name of collection to be created. Options is a document and is used to specify configuration of collection.

Parameter Type Description
Name String Name of the collection to be created
Options Document (Optional) Specify options about memory size and indexing

Options parameter is optional, so you need to specify only the name of the collection. Following is the list of options you can use −

Field Type Description
capped Boolean (Optional) If true, enables a capped collection. Capped collection is a fixed size collection that automatically overwrites its oldest entries when it reaches its maximum size. If you specify true, you need to specify size parameter also.
autoIndexId Boolean (Optional) If true, automatically create index on _id field.s Default value is false.
size number (Optional) Specifies a maximum size in bytes for a capped collection. If capped is true, then you need to specify this field also.
max number (Optional) Specifies the maximum number of documents allowed in the capped collection.

While inserting the document, MongoDB first checks size field of capped collection, then it checks max field.

Examples

Basic syntax of createCollection() method without options is as follows −

>use test
switched to db test
>db.createCollection("mycollection")
{ "ok" : 1 }
>

You can check the created collection by using the command show collections.

>show collections
mycollection
system.indexes

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

> db.createCollection("mycol", { capped : true, autoIndexID : true, size : 6142800, max : 10000 } ){
"ok" : 0,
"errmsg" : "BSON field 'create.autoIndexID' is an unknown field.",
"code" : 40415,
"codeName" : "Location40415"
}
>

In MongoDB, you don't need to create collection. MongoDB creates collection automatically, when you insert some document.

>db.howcodex.insert({"name" : "howcodex"}),
WriteResult({ "nInserted" : 1 })
>show collections
mycol
mycollection
system.indexes
howcodex
>
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