Day 10 : Delete document in MongoDB

1. Create database in mongodb
2. Create collection in mongodb
3. Create document in mongodb
4. query document in mongodb
5. update document in mongodb
6. Projections in mongodb
7. Sort records in mongodb
8. Delete document in mongodb
9. drop collection in mongodb
10. drop database in mongodb

In this part of the Learn Mongo Series, we will learn how to delete a document in mongodb.

We can delete a document in mongodb using the remove() command. remove() method in mongodb takes 2 parameters which are explained below :

• Criteria : We pass the deletion criteria on the basis of which documents will be deleted.
• Flag : If this flag is 1 or true , then only the first occurrence of the documents matching the deletion criteria is deleted.

There are 3 ways to remove the documents using the remove() method which are :

Consider the following dataset for the operations :


										
> use students
switched to db students
> db.details.find().pretty()
{
        "_id" : ObjectId("5996be4fa4b26dc0d6d75c1c"),
        "name" : "nodejsera",
        "age" : "10",
        "description" : "Mongodb tuttorial series"
}
{
        "_id" : ObjectId("5996be4fa4b26dc0d6d75c1e"),
        "name" : "b",
        "age" : "12",
        "description" : "something "
}
{
        "_id" : ObjectId("5996be4fa4b26dc0d6d75c1d"),
        "age" : "11",
        "description" : "learn mongodb",
        "name" : "a"
}
{
        "_id" : ObjectId("5996be4fa4b26dc0d6d75c1f"),
        "name" : "nodejsera",
        "age" : "13",
        "description" : "Express tutorial series"
}
>

										
									



1. Remove all documents : If we want to remove all the documents from the collection then we can use db.collection_name.remove() command as shown below :
   

   											
   > use students
   switched to db students
   > db.details.remove()
   >
   
   											
   										

   
   It will remove all the documents from the details collection.
2. Remove all documents matching a deletion_Criteria : If we want to remove all the documents which matches a certain criteria, then we can use db.collection_name.remove(Deletion_criteria) command as shown below :
   

   											
   > use students
   switched to db students
   > db.details.remove({'name':'nodejsera'})
   >  db.details.find().pretty()
   {
           "_id" : ObjectId("5996be4fa4b26dc0d6d75c1e"),
           "name" : "b",
           "age" : "12",
           "description" : "something "
   }
   {
           "_id" : ObjectId("5996be4fa4b26dc0d6d75c1d"),
           "age" : "11",
           "description" : "learn mongodb",
           "name" : "a"
   }
   >
   
   											
   										

   
   If you observe, all the documents matching the deletion criteria are removed.
3. Remove the first occurrence of the documents matching the deletion criteria: If we want to delete the first occurrence of the document matching the deletion criteria , then we can use db.collection_name.remove(Deletion_criteria,1) command as shown below :
   

   											
   > use students
   switched to db students
   > db.details.remove({'name':'nodejsera'},1)
   >  db.details.find().pretty()
   {
           "_id" : ObjectId("5996be4fa4b26dc0d6d75c1e"),
           "name" : "b",
           "age" : "12",
           "description" : "something "
   }
   {
           "_id" : ObjectId("5996be4fa4b26dc0d6d75c1d"),
           "age" : "11",
           "description" : "learn mongodb",
           "name" : "a"
   }
   {
           "_id" : ObjectId("5996be4fa4b26dc0d6d75c1f"),
           "name" : "nodejsera",
           "age" : "13",
           "description" : "Express tutorial series"
   }
   >
   
   											
   										

   
   
Hurray !! Mission Accomplished. We have successfully removed the documents from mongodb collections.

In this part of learn mongo series , we learned about how we can remove documents from mongodb collection. We learned the following commands of mongodb :

1. use : This command is use to either create a new database or switch to an already existing database.
2. db.Collection_name.find().pretty() : This command is used to list all the documents from the collection
3. db.Collection_name.remove() : This command is used to remove all the documents from the collection.
4. db.Collection_name.remove({Deletion_Criteria}) : This command is used to remove all the documents from the collection which matches deletion criteria.
5. db.Collection_name.remove({Deletion_Criteria},1) : This command is used to remove the first occurrence of the document from the collection whcih macthes deletion criteria.