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"
]
}
}
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]}}).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"
]
}
}
}
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]}})
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"
]
}
}
}
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".
Source: http://www.w3resource.com/mongodb/mongodb-mod-operators.php ?
