The deleteOne() method in MongoDB deletes the first document from the collection that matches the given selection criteria. It will delete/remove a single document from the collection.
If you use this method in the capped collection, then this method will give a WriteError exception, so to delete documents from the capped collection use the drop() method.
If you use this method in the sharded collection, then the query expression passed in this method must contain the sharded key/_id field, if not then this method will give an error. You can also use this method in multi-document transactions.
Syntax
db.Collection_name.deleteOne(
selection_criteria:<document>,
{
writeConcern: <document>,
collation: <document>,
hint: <document|string>
})
Parameter
- Selection criteria: Specifies criteria to delete documents. The type of this parameter is a document.
Optional Parameters
- writeConcern: It is only used when you do not want to use the default write concern. The type of this parameter is a document.
- Collation: It specifies the use of the collation for operations. It allows users to specify the language-specific rules for string comparison like rules for lettercase and accent marks. The type of this parameter is a document.
- hint: It is a document or field that specifies the index to use to support the filter. It can take an index specification document or the index name string and if you specify an index that does not exist, then it will give an error.
Return
This method returns a document that contains the following fields:
- acknowledged: It is a boolean field, if the value of this field is true then the operation run with write concern. If the value of this field is false, then the operation runs without write concern.
- deleteCount: This field contains the total number of deleted documents.
MongoDB deleteOne Method Examples
Let’s look at some examples of the deleteOne method in MongoDB.
In the following examples, we are working with:
Database: gfg
Collections: student
Document: Four documents contains the name and the age of the students
Delete One Document that Match Selection Criteria Example
Delete the first matched document whose age is 17:
db.student.deleteOne({age:17})Here, we delete the first document that matches the filter query(i.e., age:17) from the student collection using the deleteOne() method.
After deletion:
Example 2
Delete the first matched document whose age is less than 18:
db.student.deleteOne({age:{$lt:18}})Here, we delete the first document that matches the filter query(i.e., {age:{$lt:18}}) from the student collection using the deleteOne() method.
Note: $lt operator means less than.
After deletion:
Conclusion
The deleteOne method in MongoDB is used to delete a single document from a collection. The deleteOne method only deletes the document that matches the selection criteria.
We have explained the method with simple definitions and examples. The examples demonstrate different use cases of the db.Collection_name.deleteOne() method.