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Querying array elements with MongoDB?
MongoDB is better when you are querying array elements. Let us use the following syntax for querying array elements −
db.yourCollectionName.find({yourArrayFieldName:"yourValue"}).pretty();
The above syntax will return all those documents which have the value “yourValue” in an array field.
To understand the concept, let us create a collection with the document. The query to create a collection with a document is as follows −
> db.queryArrayElementsDemo.insertOne({ ... "StudentName":"John","StudentFavouriteSubject":["C","Java"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c90c0354afe5c1d2279d694") } > db.queryArrayElementsDemo.insertOne({ "StudentName":"Carol","StudentFavouriteSubject":["C","C++"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c90c0434afe5c1d2279d695") } > db.queryArrayElementsDemo.insertOne({ "StudentName":"David","StudentFavouriteSubject":["MongoDB","Java"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c90c0584afe5c1d2279d696") }
Display all documents from a collection with the help of find() method. The query is as follows −
> db.queryArrayElementsDemo.find().pretty();
The following is the output −
{ "_id" : ObjectId("5c90c0354afe5c1d2279d694"), "StudentName" : "John", "StudentFavouriteSubject" : [ "C", "Java" ] } { "_id" : ObjectId("5c90c0434afe5c1d2279d695"), "StudentName" : "Carol", "StudentFavouriteSubject" : [ "C", "C++" ] } { "_id" : ObjectId("5c90c0584afe5c1d2279d696"), "StudentName" : "David", "StudentFavouriteSubject" : [ "MongoDB", "Java" ] }
Querying array elements with MongoDB −
> db.queryArrayElementsDemo.find({StudentFavouriteSubject:"Java"}).pretty();
The following is the output −
{ "_id" : ObjectId("5c90c0354afe5c1d2279d694"), "StudentName" : "John", "StudentFavouriteSubject" : [ "C", "Java" ] } { "_id" : ObjectId("5c90c0584afe5c1d2279d696"), "StudentName" : "David", "StudentFavouriteSubject" : [ "MongoDB", "Java" ] }
Look at the above sample output, the above query returns all those documents with the value “Java”.
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