Unit 13 - Modifying Query Results

Modifying Query Results

Sorting and Limiting Query Results in MongoDB

cursor is the pointer to the result set of a query. the find() method returns a cursor.

cursor methods

chained the queries, perform actions on the result set.

cursor.sort() method is used to sort the result in ascending or descending order.

db.collection.find(<query>).sort(<sort>);

cursor.limit() method is used to limit the number of documents returned by a query.

db.companies.find(<query>).limit(<number>);

Sample

find compainies that category is music and sort by name in ascending order

db.companies
    .find({ category_code: "music" })
    .sort({ name: 1 });

1 for ascending order, -1 for descending order.

Limiting the Number of Documents Returned

limit the number of documents returned by a query will improve the performance of the query.

db.companies
    .find({ category_code: "music" }, { name: 1, number_of_employees: 1 })
    .sort({ number_of_employees: -1 })
    .limit(3);

Sample

db.sales
.find({ "items.name": { $in: ["laptop", "backpack", "printer paper"] }, "storeLocation": "London", })
.sort({ saleDate: -1, })
.limit(3)

Return Specific Fields(DTO) in Query Results