How to print nested array using mongo query

Question

I'm trying to print the values of an nested array.But getting execute script error.How do I print object BSON and avoid error in for nested array. Note : I want to do with print and not find().

Customer schema

 {
 "name" : "Sam",   
 "phone" : [ 
 {
   "home" : "123456",
  "work" : "045842"
 }]}

query

db.getCollection('customer').find({}).forEach( function(cust) 
{
print("Customer Name : " + cust.name); // prints Sam
print("Home Contact : " + cust.phone) // prints [object BSON]
print("Home Contact : " + cust.phone.home) // throws error
});

gbackmania · Accepted Answer · 2018-12-21 04:54:28Z

1

You could use aggregation if there are multiple items in the array

 db.collectionName.aggregate([

    { $unwind: { path: "$phone", preserveNullAndEmptyArrays: true}},

 ]).forEach(function(doc){

    print(doc.name)
    if(doc.phone !== undefined) print(doc.phone.home)
    if(doc.phone !== undefined) print(doc.phone.work)
 })

answered Dec 21, 2018 at 4:54

gbackmania

8903 gold badges9 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Nalu Over a year ago

Thanks. Can you explain what is the actual purpose of aggregate and what does unwind here mean { $unwind: { path: "$phone", preserveNullAndEmptyArrays: true}},

gbackmania Over a year ago

Aggregate takes in a series of stages that can slice and dice the data for analysis. $unwind is a one of the many stages provided by the MongoDB aggregation framework. Check out this blog about aggregation 101 - blog.appriver.com/dev/…

Nuno Sousa · Accepted Answer · 2018-12-20 21:09:23Z

1

You just need to convert the object to string and access the array;

   print("Home Contact : " + JSON.stringify(cust.phone[0])) 
    // prints ` Home Contact: { "home" : "123456", "work" : "045842" }
   print("Home Contact : " + cust.phone[0].home) // "123456"

An example:

aireclaimRs:PRIMARY> use test
switched to db test
aireclaimRs:PRIMARY> db.createCollection('customer')
{ "ok" : 1 }
aireclaimRs:PRIMARY> db.customer.insert( {
...  "name" : "Sam",   
...  "phone" : [ 
...  {
...    "home" : "123456",
...   "work" : "045842"
...  }]})
WriteResult({ "nInserted" : 1 })
aireclaimRs:PRIMARY> db.getCollection('customer').find().forEach(function(cust){
... print("Customer Name : " + cust.name);
... print("Homes Contact : " + JSON.stringify(cust.phone[0]));
... print("Home Contact : " + cust.phone[0].home)
... })
Customer Name : Sam
Homes Contact : {"home":"123456","work":"045842"}
Home Contact : 123456

edited Dec 20, 2018 at 21:09

answered Dec 20, 2018 at 19:48

Nuno Sousa

8927 silver badges16 bronze badges

3 Comments

Nalu Over a year ago

Thanks for the answer. I tried them. print("Home Contact : " + JSON.stringify(cust.phone[0])) and print("Home Contact : " + cust.phone[0].home) is not working. Only this works.... print("Home Contact : " + JSON.stringify(cust.phone))

Nuno Sousa Over a year ago

They really SHOULD work, both of them: I've edited the answer

Nalu Over a year ago

Thanks. I had some records with empty phone array (basically data issue). So i added a if condition like if(cust.phone){.....code} , and then your solution worked. Thanks once again.

Collectives™ on Stack Overflow

How to print nested array using mongo query

2 Answers 2

2 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related