The simple method of using distinct to MongoDB in the _mongodb

The destinct command for MongoDB is to get a list of different values in a particular field. This command applies to normal fields, array fields, and arrays of embedded documents.

MongoDB's distinct statement:

Copy Code code as follows:

Db.users.distinct (' last_name ')

Equivalent to an SQL statement:

Copy Code code as follows:

Select DISTINCT last_name from Users

Represents the return of a different recordset based on the specified field.
A simple example:

 
> Db.addresses.insert ({"Zip-code": 10010}) 
> Db.addresses.insert ({"Zip-code": 10010}) 
> Db.addresses.insert ({"Zip-code": 99701}) 
 
>//Shell helper: 
> Db.addresses.distinct ("Zip-code"); 
[10010, 99701] 
 
>//Running as a command manually: 
> Db.runcommand ({distinct: ' Addresses ', key: ' Zip-code '}) 
{"Values" : [10010, 99701], "OK" 
// 
> Db.comments.save ({"user": {"Points":}}) 
> Db.comments.save ({"User ': {' points ': [to}}] 
> Db.comments.save ({"user": {"Points":}}) 
 
> db.comments.distinct ("user.points "); 
[25, 31]

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