mongodb
Khóa học miễn phí MongoDB – Create Collection nhận dự án làm có lương
MongoDB – Create Collection
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.tutorialspoint.insert({"name" : "tutorialspoint"}),
WriteResult({ "nInserted" : 1 })
>show collections
mycol
mycollection
system.indexes
tutorialspoint
>
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