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How to use MongoDB $pull to delete documents within an Array?
You need to use update command along with $pull operator to delete documents within an array. Let us create a collection with documents. Following is the query
> db.deleteDocumentsDemo.insertOne( ... { ... "_id":100, ... "StudentsDetails" : [ ... { ... "StudentId" : 1, ... "StudentName" : "John" ... }, ... { ... "StudentId" : 2, ... "StudentName" : "Carol" ... }, ... { ... "StudentId" : 3, ... "StudentName" : "Sam" ... }, ... { ... "StudentId" : 4, ... "StudentName" : "Mike" ... } ... ] ... } ... ... ); { "acknowledged" : true, "insertedId" : 100 } > db.deleteDocumentsDemo.insertOne( ... { ... "_id":200, ... "StudentsDetails" : [ ... { ... "StudentId" : 5, ... "StudentName" : "David" ... }, ... { ... "StudentId" : 6, ... "StudentName" : "Ramit" ... }, ... { ... "StudentId" : 7, ... "StudentName" : "Adam" ... }, ... { ... "StudentId" : 8, ... "StudentName" : "Larry" ... } ... ] ... } ... ... ); { "acknowledged" : true, "insertedId" : 200 }
Following is the query to display all documents from a collection with the help of find() method
> db.deleteDocumentsDemo.find().pretty();
This will produce the following output
{ "_id" : 100, "StudentsDetails" : [ { "StudentId" : 1, "StudentName" : "John" }, { "StudentId" : 2, "StudentName" : "Carol" }, { "StudentId" : 3, "StudentName" : "Sam" }, { "StudentId" : 4, "StudentName" : "Mike" } ] } { "_id" : 200, "StudentsDetails" : [ { "StudentId" : 5, "StudentName" : "David" }, { "StudentId" : 6, "StudentName" : "Ramit" }, { "StudentId" : 7, "StudentName" : "Adam" }, { "StudentId" : 8, "StudentName" : "Larry" } ] }
Following is the query to delete documents within an array
> db.deleteDocumentsDemo.update({}, ... {$pull: {StudentsDetails: {StudentName: "David"}}}, ... {multi: true}); WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 1 })
Let us check the documents are deleted or not. Following is the query
> db.deleteDocumentsDemo.find().pretty();
This will produce the following output
{ "_id" : 100, "StudentsDetails" : [ { "StudentId" : 1, "StudentName" : "John" }, { "StudentId" : 2, "StudentName" : "Carol" }, { "StudentId" : 3, "StudentName" : "Sam" }, { "StudentId" : 4, "StudentName" : "Mike" } ] } { "_id" : 200, "StudentsDetails" : [ { "StudentId" : 6, "StudentName" : "Ramit" }, { "StudentId" : 7, "StudentName" : "Adam" }, { "StudentId" : 8, "StudentName" : "Larry" } ] }
Look at the above sample output, the “StudentId” with value 5 i.e. StudentName “David” have been deleted.
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