Category: MongoDB

MongoDB

Remove Documents using Mongo Shell

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The db.collection.remove() method removes documents from a collection.

  • You can remove all documents from a collection.
  • Remove all documents that match a condition.
  • Or limit the operation to remove just a single document.
 db.users.remove({})  //Remove All Documents  
 db.users.remove({Name : "Himen Patel" })  //Remove Documents that Match a Condition  
 db.users.remove({Name : "Himen Patel" },1 )  //Remove a Single Document that Matches a Condition
MongoDB

Upsert Option using Mongo Shell

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By default, if no document matches the update query, the update() method does nothing.

However, by specifying upsert: true, the update() method either updates matching document or documents, or inserts a new document using the update specification if no matching document exists.

The following operation either updates a matching document by replacing it with a new document or adds a new document if no matching document exists.

 > db.users.update(  
 ...  { Name : "Hymen Patel" },  
 ...    {  
 ...  "Name": "Himen Paatel",  
 ...  "Email": "email2himen@dotnet-funda.com",  
 ...  "Address1": "1257 Commons Drive",  
 ...  "City": "Cooperstown",  
 ...  "Zip Code": "13326",  
 ...  "Country": "USA"  
 ...    },  
 ... { upsert: true }  
 ... )

The update operation returns a WriteResult object which contains the status of the operation, including whether the db.collection.update() method modified an existing document or added a new document.

 WriteResult({  
     "nMatched" : 0,  
     "nUpserted" : 1,  
     "nModified" : 0,  
     "_id" : ObjectId("561324b1b6bb748311f00aac")  
 })

Specify upsert: true for the update specific fields operation

 db.users.update(   
      { Name : "Himen Patel" },   
        {$set :   
        { "Email" : "admin@dotnet-fundamentals.com"} },  
       {upsert: true}  
 )
MongoDB

Replace a document using Mongo Shell

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The following operation replaces the document with item equal to “Himen Patel”. The newly replaced document will only contain the the _id field and the fields in the replacement document.

 > db.users.update(  
 ...  { Name : "Himen Patel" },  
 ...    {  
 ...  "Name": "Himen Paatel",  
 ...  "Email": "email2himen@dotnet-funda.com",  
 ...  "Address1": "1257 Commons Drive",  
 ...  "City": "Cooperstown",  
 ...  "Zip Code": "13326",  
 ...  "Country": "USA"  
 ...    }  
 ... )

A successful update of the document returns the following object.

 WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
MongoDB

Modify Documents using Mongo Shell

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MongoDB provides the update() method to update the documents of a collection. The method accepts as its parameters:

  • an update conditions document to match the documents to update,
  • an update operations document to specify the modification to perform, and
  • an options document.

To specify the update condition, use the same structure and syntax as the query conditions.

 > db.users.update( { Name : "Himen Patel" }, {$set : { "Email" : "admin@dotnet-fundamentals.com"} })

A successful update of the document returns the following object:

 WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })


Update multiple documents.
By default, the update() method updates a single document. To update multiple documents, use the multi option in the update() method.

 db.users.update( { Name : "Himen Patel" }, {$set : { "Email" : "admin@dotnet-fundamentals.com"} }, {multi: true})

A successful update of the document returns the following object.

 WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 1 })