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Mongodb Tutorial

MongoDB: db.collection.distinct() method

db.collection.dataSize

The db.collection.distinct() method is used to find the distinct values for a specified field across a single collection and returns the results in an array.

Syntax:

db.collection.distinct(field, query)

Parameters:

Name Description Required /
Optional
Type
field The field for which to return distinct values. Required string
query A query that specifies the documents from which to retrieve the distinct values. Required document

Sample document in the restaurants collection:


{
  "address": {
     "building": "1007",
     "coord": [ -73.856077, 40.848447 ],
     "street": "Morris Park Ave",
     "zipcode": "10462"
  },
  "borough": "Bronx",
  "cuisine": "Bakery",
  "grades": [
     { "date": { "$date": 1393804800000 }, "grade": "A", "score": 2 },
     { "date": { "$date": 1378857600000 }, "grade": "A", "score": 6 },
     { "date": { "$date": 1358985600000 }, "grade": "A", "score": 10 },
     { "date": { "$date": 1322006400000 }, "grade": "A", "score": 9 },
     { "date": { "$date": 1299715200000 }, "grade": "B", "score": 14 }
  ],
  "name": "Morris Park Bake Shop",
  "restaurant_id": "30075445"
}
............

Example: Return Distinct Values for a Field

The following example returns the distinct values for the field cuisine  from all documents in the restaurants collection:

db.restaurants.distinct( "cuisine" );

Output:

The method returns the following array of distinct cuisine values:

[
        "Irish",
        "Bakery",
        "American ",
        "Hamburgers",
        "Jewish/Kosher",
        "Delicatessen",
        "Ice Cream, Gelato, Yogurt, Ices",
        "Chinese",
        "Other",
        "Chicken",
        "Turkish",
        "Caribbean",
        "Donuts",
        "Sandwiches/Salads/Mixed Buffet",
        "Bagels/Pretzels",
        "Pizza",
        "Italian",
        "Steak",
        "Continental",
        "Latin (Cuban, Dominican, Puerto Rican, South & Central American)",
        "Polish",
        "German",
        "French",
        "Pizza/Italian",
        "Mexican",
        "Spanish",
        "Café/Coffee/Tea",
        "Tex-Mex",
        "Pancakes/Waffles",
        "Soul Food",
        "Seafood",
        "Hotdogs",
        "Greek",
        "Not Listed/Not Applicable",
        "African",
        "Japanese",
        "Indian",
        "Armenian",
        "Thai",
        "Chinese/Cuban",
        "Mediterranean",
        "Korean",
        "Bottled beverages, including water, sodas, juices, etc.",
        "Russian",
        "Eastern European",
        "Middle Eastern",
        "Asian",
        "Ethiopian",
        "Vegetarian",
        "Barbecue",
        "Egyptian",
        "English",
        "Sandwiches",
        "Portuguese",
        "Indonesian",
        "Chinese/Japanese",
        "Filipino",
        "Juice, Smoothies, Fruit Salads",
        "Brazilian",
        "Afghan",
        "Vietnamese/Cambodian/Malaysia",
        "Café/Coffee/Tea",
        "Soups & Sandwiches",
        "Tapas",
        "Moroccan",
        "Pakistani",
        "Peruvian",
        "Bangladeshi",
        "Czech",
        "Salads",
        "Creole",
        "Fruits/Vegetables",
        "Iranian",
        "Cajun",
        "Scandinavian",
        "Polynesian",
        "Soups",
        "Australian",
        "Hotdogs/Pretzels",
        "Southwestern",
        "Nuts/Confectionary",
        "Hawaiian",
        "Creole/Cajun",
        "Californian",
        "Chilean"
]

Example: Return Distinct Values for an Embedded Field

The following example returns the distinct values for the field zipcode, embedded in the address field, from all documents in the restaurants collection:

db.restaurants.distinct( "address.zipcode" );

Output:

The method returns the following array of distinct zipcode values:

[
        "10019",
        "10462",
        "11224",
        "11225",
        "11374",
        "11369",
        "11219",
        "11234",
        "10460",
        "11226",
        "11214",
        "11208",
        "10065",
        "11223",
        "11414",
        "11218",
        "11004",
        "11209",
        "11215",
        "10021",
        "11356",
        "10314",
        "10003",
        "11106",
        "10024",
        "10025",
        "10012",
        "10005",
        "11368",
        "11203",
        "11205",
        "10466",
        "10007",
        "11201",
        "10018",
        "10474",
        "10174",
        "11418",
        "11379",
        "10016",
        "10022",
        "11236",
        "11385",
        "11212",
        "10023",
        "11230",
        "11371",
        "10306",
        "10458",
        "10308",
        "10038",
        "11211",
        "10028",
        "10017",
        "10465",
        "10014",
        "11222",
        "10013",
        "11101",
        "10009",
        "10305",
        "11235",
        "10011",
        "11363",
        "11232",
        "11103",
        "10309",
        "10032",
        "11228",
        "10036",
        "10033",
        "10451",
        "11372",
        "11366",
        "11204",
        "10312",
        "10001",
        "10467",
        "11435",
        "11432",
        "11001",
        "10302",
        "11229",
        "11694",
        "11420",
        "11697",
        "11367",
        "10463",
        "11375",
        "10006",
        "10452",
        "11427",
        "10475",
        "11373",
        "10310",
        "10304",
        "11238",
        "10010",
        "11105",
        "11377",
        "10034",
        "11360",
        "11415",
        "11416",
        "10470",
        "11354",
        "10301",
        "10002",
        "11361",
        "11358",
        "11213",
        "10128",
        "10464",
        "10004",
        "11239",
        "11104",
        "11231",
        "10075",
        "11364",
        "11237",
        "11249",
        "11362",
        "11357",
        "10303",
        "11434",
        "10472",
        "11220",
        "11378",
        "10461",
        "11417",
        "10027",
        "11365",
        "11413",
        "10029",
        "10459",
        "11421",
        "10468",
        "11217",
        "11216",
        "10456",
        "11423",
        "11207",
        "11355",
        "10469",
        "11206",
        "10455",
        "10454",
        "11210",
        "10119",
        "10020",
        "10453",
        "11412",
        "11419",
        "11429",
        "11370",
        "10040",
        "11430",
        "11221",
        "11422",
        "11428",
        "11040",
        "11693",
        "11411",
        "10031",
        "11691",
        "10457",
        "11102",
        "10037",
        "10106",
        "10030",
        "10471",
        "10112",
        "11426",
        "10039",
        "10035",
        "11005",
        "10307",
        "11692",
        "10044",
        "10026",
        "10280",
        "11233",
        "10103",
        "10121",
        "10282",
        "10473",
        "10281",
        "11436",
        "10153",
        "11433",
        "10057",
        "11242",
        "10111",
        "10122",
        "10168",
        "10107",
        "10000",
        "11109",
        "10171",
        "11256",
        "10069",
        "10311",
        "11010",
        "11451",
        "07005",
        "10317",
        "10104",
        "",
        "10048",
        "10123",
        "11352",
        "10165",
        "10167"
]

Example: Specify Query with distinct

The following example returns the distinct values for the field zipcode, embedded in the address field, from the documents whose cuisine is equal to "Delicatessen":

db.restaurants.distinct( "address.zipcode" , { "cuisine" : "Delicatessen" } );

Output:

The method returns the following array of distinct zipcode values:

[
        "11234",
        "11209",
        "11356",
        "10003",
        "11106",
        "10314",
        "11385",
        "10306",
        "10308",
        "10021",
        "10022",
        "10006",
        "10475",
        "10007",
        "10017",
        "10019",
        "11101",
        "11215",
        "10018",
        "10036",
        "11365",
        "10001",
        "10025",
        "11426",
        "11228",
        "11360",
        "10012",
        "11357",
        "11370",
        "10016",
        "10028",
        "10309",
        "11694",
        "10310",
        "11377",
        "10013",
        "10463",
        "11375",
        "10002",
        "11363",
        "11217",
        "11361",
        "10004",
        "10282",
        "11364",
        "10038",
        "11105",
        "10464",
        "11378",
        "10458",
        "11222",
        "11220",
        "10065",
        "11232",
        "11415",
        "11242",
        "11354",
        "11103",
        "10023",
        "10451",
        "10014",
        "11208",
        "10112",
        "11417",
        "10032",
        "11430",
        "11432",
        "10024",
        "10020",
        "11238",
        "10005",
        "10011",
        "11369",
        "10467",
        "11230",
        "11231",
        "10455",
        "10010",
        "11379",
        "11201",
        "11355",
        "11219",
        "11368",
        "10033",
        "11214",
        "11102",
        "10027",
        "10301",
        "10280",
        "11434",
        "11372",
        "10469",
        "11206",
        "10029",
        "11435",
        "10461",
        "10468",
        "10474",
        "11423",
        "10075",
        "11416",
        "10462",
        "10302",
        "11236",
        "10312",
        "11414",
        "11223",
        "10035",
        "11374",
        "11367",
        "10128",
        "11422",
        "10465",
        "11237",
        "11418",
        "10453",
        "11207"
]

Retrieve the restaurants data from here

Behavior

Array Fields

If the value of the specified field is an array, db.collection.distinct() considers each element of the array as a separate value.

For instance, if a field has as its value [ 1, [1], 1 ], then db.collection.distinct() considers 1, [1], and 1 as separate values.

Index Use

When possible, db.collection.distinct() operations can use indexes.

Indexes can also cover db.collection.distinct() operations.

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