是否可以仅获取 MongoDB 文档的特定字段的值？

Question

For example, I have a collection of documents: [{id:1, title:'A'}, {id:2, title:'B'}, ...]

I want to fetch documents based on some conditions, and only get the values of the fields I want instead of the whole object. In SQL, this can be done by SELECT title FROM documents WHERE year = 2020

Can I achieve similar results in MongoDB with PyMongo?

Answer 1

Try projection like this

$cursor = $db->inventory->find(
    ['status' => 'A'],
    ['projection' => ['item' => 1, 'status' => 1]]
);

Answer 2

.find() in MongoDB will have this syntax .find(filter_part, projection_part) , You can try below code in pymongo:

Code:

/** As `.find()` returns a cursor you can iterate on it to get values out,
 *  In projection `_id` is by default included, So we need to exclude it, projection can use True/False or 1/0 */

for eachDocument in collection.find({year : 2020}, {title: True, _id : False}):
      print(eachDocument)