MongoDB: Find Single Document from Collection using findOne()
In MongoDB, a collection represents a table in RDBMS and a document is like a record in a table. Here you will learn how to retrieve or find a single document from a collection.
MongoDB provides two methods for finding documents from a collection:
- findOne() - returns a the first document that matched with the specified criteria.
- find() - returns a cursor to the selected documents that matched with the specified criteria.
The following inserts documents in the employees
collection.
db.employees.insertMany([
{
_id:1,
firstName: "John",
lastName: "King",
email: "[email protected]",
salary: 5000
},
{
_id:2,
firstName: "Sachin",
lastName: "T",
email: "[email protected]",
salary: 8000
},
{
_id:3,
firstName: "James",
lastName: "Bond",
email: "[email protected]",
salary: 7500
},
{
_id:4,
firstName: "Steve",
lastName: "J",
email: "[email protected]",
salary: 9000
},
{
_id:5,
firstName: "Kapil",
lastName: "D",
email: "[email protected]",
salary: 4500
},
{
_id:6,
firstName: "Amitabh",
lastName: "B",
email: "[email protected]",
salary: 11000
}
])
findOne()
The findOne()
method returns the first document that is matched with the specified criteria.
Syntax:
db.collection.findOne(query, projection)
Parameters:
- query: Optional. Specifies the criteria using query operators.
- projection: Optional. Specifies the fields to include in a resulted document.
The findOne()
returns the first document from a collection if no parameter is passed.
db.employees.findOne()
{
_id: 1,
firstName: 'John',
lastName: 'King',
email: '[email protected]',
salary: 5000
}
Specify a criteria as { field: "value", field:"value",..}
on which you want to find a document. For example, the following returns a document where firstName
field is "Kapil".
db.employees.findOne({firstName: "Kapil"})
{
_id: 5,
firstName: 'Kapil',
lastName: 'D',
email: '[email protected]',
salary: 4500
}
The findOne()
method performs the case-sensitive search, so {firstName: "Kapil"}
and {firstName: "kapil"}
returns different result.
It returns null if it cannot find a document matching the specified criteria.
db.employees.findOne({_id:10})
null
Use the query operators for more refined search. For example, the following finds the first document where salary is greater than 8000.
db.employees.findOne({salary: {$gt: 8000}})
{
_id: 4,
firstName: 'Steve',
lastName: 'J',
email: '[email protected]',
salary: 9000
}
In the above example, the query operator criteria for the salary
field is written inside another document as {field: {operator: value}}
. The {salary: {$gt: 8000}}
criteria returns the first document where salary
is greater than 8000
.
Projection
Use the projection parameter to specify the fields to be included in the result. The projection parameter format is {<field>: <1 or true>, <field>: <1 or true>...}
where 1 or true includes the field, and o or false excludes the field in the result.
db.employees.findOne({firstName: "Sachin"}, {firstName:1, lastName:1})
{ _id: 2, firstName: 'Sachin', lastName: 'T' }
Note that by default, the _id
field will be included in the result. To omit it, specify { _id:0 }
in the projection.
db.employees.findOne({firstName: "Sachin"}, {_id: 0, firstName:1, lastName:1})
{ firstName: 'Sachin', lastName: 'T' }