mongodb select one field
跳到 Return Distinct Values for an Array Field. - The following example returns the distinct values for the field sizes from all documents in the ... ,To return all documents in a collection, omit this parameter or pass an empty ..... The query uses dot notation to access fields in an embedded document: copy. ,Omit this parameter to return all fields in the matching document. The <boolean> can be one of the following include or exclude values: 1 or true to include. The findOne() method always includes the _id field even if the field is not explicitly spec,From the MongoDB docs: A projection can explicitly include several fields. In the following operation, find() method returns all documents that match the query. In the result set, only the item and qty fields and, by default, the _id field return in the m,db.collection.distinct('x'). should give you an array of unique values for that field. ... of docs, containing just it's x value... db.collection.find( }, x: 1, y: 0, _id:0 } ). ,Please take a look at the documentation. You will notice that find has an optional second parameter called "projection". This parameter is used to state which ... ,Still, such low-selectivity fields don't yield good index performance, because he .... In a find(), or the $match phase of aggregation, $eq takes a single value, and ... ,To limit the amount of data that MongoDB sends to applications, you can include a projection document to specify or restrict fields to return. This page provides examples of query operations with projection using the db.collection.find() method in the mon
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 mongodb select one field 相關參考資料
db.collection.distinct() — MongoDB Manual
跳到 Return Distinct Values for an Array Field. - The following example returns the distinct values for the field sizes from all documents in the ... https://docs.mongodb.com db.collection.find() — MongoDB Manual
To return all documents in a collection, omit this parameter or pass an empty ..... The query uses dot notation to access fields in an embedded document: copy. https://docs.mongodb.com db.collection.findOne() — MongoDB Manual
Omit this parameter to return all fields in the matching document. The <boolean> can be one of the following include or exclude values: 1 or true to include. The findOne() method always includes... https://docs.mongodb.com How to select a single field in MongoDB? - Stack Overflow
From the MongoDB docs: A projection can explicitly include several fields. In the following operation, find() method returns all documents that match the query. In the result set, only the item and qt... https://stackoverflow.com List all values of a certain field in mongodb - Stack Overflow
db.collection.distinct('x'). should give you an array of unique values for that field. ... of docs, containing just it's x value... db.collection.find( }, x: 1, y: 0, _id:0 } ). https://stackoverflow.com mongo .find return specific field only for all user - Stack Overflow
Please take a look at the documentation. You will notice that find has an optional second parameter called "projection". This parameter is used to state which ... https://stackoverflow.com Mongodb query with fields in the same documents - Stack Overflow
Still, such low-selectivity fields don't yield good index performance, because he .... In a find(), or the $match phase of aggregation, $eq takes a single value, and ... https://stackoverflow.com Project Fields to Return from Query - MongoDB Documentation
To limit the amount of data that MongoDB sends to applications, you can include a projection document to specify or restrict fields to return. This page provides examples of query operations with proj... https://docs.mongodb.com |