w3resource

MongoDB Evaluation Query operator - $mod

Description

The $mod operator is used to help the user to retrieve documents from a collection for a specific field that consist an even or odd number. This can be done easily because the $mod operator calculate the remainder and checks whether it is 0 or not. It works like 'where' clause of Sql.

If no parameter with $mod is used which behaves like a 'where' clause, results will appear where the remainder is 0 otherwise no results is displayed.

The $mod operator works only on integer values and not a strings type numeric value.

Our database name is 'myinfo' and our collection name is 'testtable'. Here, is the collection bellow.

Sample collection "testtable"

{
        "_id" : ObjectId("528f4e630fe5e6467e58ae7b"),
        "user_id" : "user1",
        "password" : "1a2b3c",
        "sex" : "Male",
        "age" : 17,
        "date_of_join" : "16/10/2010",
        "education" : "M.C.A.",
        "profession" : "CONSULTANT",
        "interest" : "MUSIC",
        "extra" : {
                "community_name" : [
                        "MODERN MUSIC",
                        "CLASSICAL MUSIC",
                        "WESTERN MUSIC"
                ],
                "community_moder_id" : [
                        "MR. Alex",
                        "MR.   Dang",
                        "MR Haris"
                ],
                "community_members" : [
                        700,
                        200,
                        1500
                ],
                "friends" : {
                        "valued_friends_id" : [
                                "kumar",
                                "harry",
                                "anand"
                        ],
                        "ban_friends_id" : [
                                "Amir",
                                "Raja",
                                "mont"
                        ]
                }
        }
}
{
        "_id" : ObjectId("528f4e720fe5e6467e58ae7c"),
        "user_id" : "user2",
        "password" : "11aa1a",
        "sex" : "Male",
        "age" : 24,
        "date_of_join" : "17/10/2009",
        "education" : "M.B.A.",
        "profession" : "MARKETING",
        "interest" : " MUSIC",
        "extra" : {
                "community_name" : [
                        "MODERN MUSIC",
                        "CLASSICAL MUSIC",
                        "WESTERN MUSIC"
                ],
                "co mmunity_moder_id" : [
                        "MR. Roy",
                        "MR. Das",
                        "MR Doglus"
                ],
                "community_members" : [
                        500,
                        300,
                        1400
                ],
                "friends" : {
                        "valued_friends_id" : [
                                "pal",
                                "viki",
                                "john"
                        ],
                        "ban_friends_id" : [
                                "jalan",
                                "mono j",
                                "evan"
                        ]
                }
        }
}
{
        "_id" : ObjectId("528f4e7e0fe5e6467e58ae7d"),
        "user_id" : "user3",
        "password" : "b1c1d1",
        "sex" : "Female",
        "age" : 19,
        "date_of_join" : "16/10/2010",
        "education" : "M.C.A.",
        "profession" : "IT COR.",
        "interest" : "AR T",
        "extra" : {
                "community_name" : [
                        "MODERN ART",
                        "CLASSICAL ART",
                        "WESTERN ART"
                ],
                "community_mo der_id" : [
                        "MR. Rifel",
                        "MR. Sarma",
                        "MR Bhatia"
                ],
                "community_members" : [
                        5000,
                        2000,
                        1500
                ],
                "friends" : {
                        "valued_friends_id" : [
                                "philip",
                                "anant",
                                "alan"
                        ],
                        "ban_friends_id" : [
                                "Amir",
                                "Raja",
                                "mont"
                        ]
                }
        }
}
{
        "_id" : ObjectId("528f4e910fe5e6467e58ae7e"),
        "user_id" : "user4",
        "password" : "abczyx",
        "sex" : "Female",
        "age" : 22,
        "date_of_join" : "17/8/2009",

        "education" : "M.B.B.S.",
        "profession" : "DOCTOR",
        "interest" : "SPORTS",
        "extra" : {
                "community_name" : [
                        "ATHELATIC",
                        "GAMES FAN GYES",
                        "FAVOURIT GAMES"
                ],
                "community_moder_id" : [
                        "MR. Paul",
                        "MR. Das",
                        "MR Doglus"
                ],
                "community_members" : [
                        2500,
                        2200,
                        3500
                ],
                "friends" : {
                        "valued_friends_id" : [
                                "vinod",
                                "viki",
                                "john"
                        ],
                        "ban_friends_id" : [
                                "jalan",
                                "monoj",
                                "evan"
                        ]
                }
        }
}
{
        "_id" : ObjectId("528f4f8a0fe5e6467e58ae7f"),
        "user_id" : "user5",
        "password" : "user5",
        "sex" : "Male",
        "age" : 21,
        "date_of_join" : "17/08/2011",
        "education" : "MCA",
        "profession" : "S.W. Engineer",
        "interest" : "SPORTS",
        "extra" : {
                "community_name" : [
                        "ATHELATIC",
                        "GAMES FAN GYES",
                        "FAVOURIT GAMES"
                ]
        }
}

Document written in command prompt

MongoDB $mod operator

If we want to fetch documents from the collection "testtable" where the value of "age" field is divisible by 8, the following mongodb command can be used :

>db.testtable.find({"age" : {$mod : [8,0]}}).pretty();

N.B. find() method displays the documents in a non structured format but to display the results in a formatted way, the pretty() method can be used.

SQL equivalent command is

SELECT * 
FROM testtable 
WHERE MOD(age,8)=0; 

Output:

{
        "_id" : ObjectId("528f4e720fe5e6467e58ae7c"),
        "user_id" : "user2",
        "password" : "11aa1a",
        "sex" : "Male",
        "age" : 24,
        "date_of_join" : "17/10/2009",
        "education" : "M.B.A.",
        "profession" : "MARKETING",
        "interest" : " MUSIC",
        "extra" : {
                "community_name" : [
                        "MODERN MUSIC",
                        "CLASSICAL MUSIC",
                        "WESTERN MUSIC"
                ],
                "co mmunity_moder_id" : [
                        "MR. Roy",
                        "MR. Das",
                        "MR Doglus"
                ],
                "community_members" : [
                        500,
                        300,
                        1400
                ],
                "friends" : {
                        "valued_friends_id" : [
                                "pal",
                                "viki",
                                "john"
                        ],
                        "ban_friends_id" : [
                                "jalan",
                                "mono j",
                                "evan"
                        ]
                }
        }
}

Document written in command prompt

The above output shows, documents appears from the collection containing such a value for the "age" field which has a remainder 0 after dividing by 8. The "$mod[8]" means "age % (modulo operator) 8=0"

MongoDB $mod operator example

If we want to fetch documents from the collection "testtable" where the value of "age" field is divisible by 9, the following mongodb command can be used :

gt;db.testtable.find({"age" : {$mod : [9,0]}})

N.B. find() method displays the documents in a non structured format but to display the results in a formatted way, the pretty() method can be used.

SQL equivalent command is

SELECT * 
FROM testtable 
WHERE MOD(age,9)=0; 

The above command returns no output, because no one document holds such a value for the "age" field which can be divisible by 9.

MongoDB $mod operator using parameter

If we want to fetch documents from the collection "testtable" where the value of "age" field contain such a value which returns a remainder 2 after dividing by 5, the following mongodb command can be used :

>db.testtable.find({"age" : {$mod : [5,2]}}).pretty();

SQL equivalent command is

SELECT * 
FROM testtable 
WHERE MOD(age,5)=2; 

Output:

{
        "_id" : ObjectId("528f4e630fe5e6467e58ae7b"),
        "user_id" : "user1",
        "password" : "1a2b3c",
        "sex" : "Male",
        "age" : 17,
        "date_of_join" : "16/10/2010",
        "education" : "M.C.A.",
        "profession" : "CONSULTANT",
        "interest" : "MUSIC",
        "extra" : {
                "community_name" : [
                        "MODERN MUSIC",
                        "CLASSICAL MUSIC",
                        "WESTERN MUSIC"
                ],
                "community_moder_id" : [
                        "MR. Alex",
                        "MR.   Dang",
                        "MR Haris"
                ],
                "community_members" : [
                        700,
                        200,
                        1500
                ],
                "friends" : {
                        "valued_friends_id" : [
                                "kumar",
                                "harry",
                                "anand"
                        ],
                        "ban_friends_id" : [
                                "Amir",
                                "Raja",
                                "mont"
                        ]
                }
        }
}
{
        "_id" : ObjectId("528f4e910fe5e6467e58ae7e"),
        "user_id" : "user4",
        "password" : "abczyx",
        "sex" : "Female",
        "age" : 22,
        "date_of_join" : "17/8/2009",

        "education" : "M.B.B.S.",
        "profession" : "DOCTOR",
        "interest" : "SPORTS",
        "extra" : {
                "community_name" : [
                        "ATHELATIC",
                        "GAMES FAN GYES",
                        "FAVOURIT GAMES"
                ],
                "community_moder_id" : [
                        "MR. Paul",
                        "MR. Das",
                        "MR Doglus"
                ],
                "community_members" : [
                        2500,
                        2200,
                        3500
                ],
                "friends" : {
                        "valued_friends_id" : [
                                "vinod",
                                "viki",
                                "john"
                        ],
                        "ban_friends_id" : [
                                "jalan",
                                "monoj",
                                "evan"
                        ]
                }
        }
}

Document written in command prompt

The above output shows, documents appears from the collection containing such a value for the "age" field which has a remainder 2 after dividing by 5. The "$mod[5,2]" means "age % (modulo operator) 5=2".

Previous: $type
Next: $regex



Inviting useful, relevant, well-written and unique guest posts