CODEWITHSUNDEEP
mysqlsqlmongodb
Mark Roberts
Mark Roberts

Reputation: 55

How do you find the most occurring field in a MongoDB dictionary?

The question might be worded improperly, but this is my problem. I have a MySQL query that finds which user has checked out the most books from a library. The SQL query works just fine, but I am brand spankin' new to the MongoDB world. Here's my SQL query:

SELECT UID, count(UID)
FROM checkout_data
GROUP BY UID
ORDER BY count(UID) desc
LIMIT 1;

How do I do this in Mongo? EDIT: Example Library

{
 "Date_Checked_Out":" 2014-01-01 09:34:36.206",
 "Day":"Wednesday",
 "Borrower_Category":" Undergraduate Student",
 "Item_Barcode":"00000000012345'",
 "Title":" Bob's Day at the Beach",
 "Material_Format":" BOOK",
 "Loan_Policy applied to item":" 0.10Day 2Week Loan",
 "Due_Date":" 2013-12-19 00:45:00.0",
 "Due_Day":"Thursday",
 "Number_times_renewed":" 0",
 "Institution":"FREED HARDEMAN UNIV; LODEN-DANIEL LIBR",
 "Home_Branch": 15243,
 "Shelving_Location":" Stacks; 1st Floor",
 "Call_Number":" BV640 .B37 1989",
 "UID":" 15243ea5-421f-4cec-b091-394586adfe2b"
}

Upvotes: 1

Views: 1871

Answers (1)

BatScream
BatScream

Reputation: 19700

This is the equivalent aggregation pipeline command:

Use the $group operator to group the records based on the UID field. Sort and then limit the first group.

   db.collection.aggregate([{
        $group: {
            "_id": "$UID",
            "count": {
                $sum: 1
            }
        }
    },
    {
        $sort: {
            "count": -1
        }
    },
    {
        $limit: 1
    }
])

Upvotes: 5

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