Get at least one match in list querying with MongoDB?

Use $in operator to get at least one match. Let us first create a collection with documents −

> db.atleastOneMatchDemo.insertOne({"StudentFavouriteSubject":["MySQL","MongoDB"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd2db5db64f4b851c3a13ce") } > db.atleastOneMatchDemo.insertOne({"StudentFavouriteSubject":["Java","C","MongoDB"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd2db71b64f4b851c3a13cf") } > db.atleastOneMatchDemo.insertOne({"StudentFavouriteSubject":["Python","C++","SQL Server"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd2db87b64f4b851c3a13d0") } >db.atleastOneMatchDemo.insertOne({"StudentFavouriteSubject":["Ruby","Javascript","C#","MySQL"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd2dba9b64f4b851c3a13d1") }

Following is the query to display all documents from a collection with the help of find() method −

> db.atleastOneMatchDemo.find().pretty();

This will produce the following output −

{    "_id" : ObjectId("5cd2db5db64f4b851c3a13ce"),    "StudentFavouriteSubject" : [       "MySQL",       "MongoDB"    ] } {    "_id" : ObjectId("5cd2db71b64f4b851c3a13cf"),    "StudentFavouriteSubject" : [       "Java",       "C",       "MongoDB"    ] } {    "_id" : ObjectId("5cd2db87b64f4b851c3a13d0"),    "StudentFavouriteSubject" : [       "Python",       "C++",       "SQL Server"    ] } {    "_id" : ObjectId("5cd2dba9b64f4b851c3a13d1"),    "StudentFavouriteSubject" : [       "Ruby",       "Javascript",       "C#",       "MySQL"    ] }

Following is the query to get at least one match −

>db.atleastOneMatchDemo.find({"StudentFavouriteSubject":{"$in":["MongoDB","MySQL"]}}).pretty();

This will produce the following output −

{    "_id" : ObjectId("5cd2db5db64f4b851c3a13ce"),    "StudentFavouriteSubject" : [       "MySQL",       "MongoDB"    ] } {    "_id" : ObjectId("5cd2db71b64f4b851c3a13cf"),    "StudentFavouriteSubject" : [       "Java",       "C",       "MongoDB"    ] } {    "_id" : ObjectId("5cd2dba9b64f4b851c3a13d1"),    "StudentFavouriteSubject" : [       "Ruby",       "Javascript",       "C#",       "MySQL"    ] }