How to update a value if not exist in mongodb

Question

db.books.find({ "status": "readED", $and: [ { "listingStatus": { $not: { $exists: true } } } ] }).forEach(function(book){ db.getSiblingDB('reading').bookListing.find({"sellerSku": book.sellerSku, "sellerId":book.seller},{"sellerId": 1, "sellerSku": 1}).forEach(function(bookListing){ printjson(bookListing); }); });

when i run this, it gives

 { "_id" : ObjectId("582cb4ad5a5a380sadas038dd2f72"), "sellerId" : "e0a82c3d-079asdas0-49asda97-aasdascdf-0c320e3d7022", "sellerSku" : "te227" } { "_id" : ObjectId("582cb4ae5a5a380038dd2f73"), "sellerId" : "e0a82casdsa3d-07asdas90-4997-acdf-0c320e3d7022", "sellerSku" : "TE231" }

so it means

there are books which is readed and listingstatus is not exist (normally listingstatus must be existed)

in reading db, there is booklisting colletion. Normally what i need to do is:

if a book readed and listingstatus is not existed, need to update listingstatus if this books sellersku exists in booklisting collection.

instead of

 printjson(bookListing);

i need to update

book.update(listingstatu) in for each but is that possible in javascript?

What aboout this

db.getSiblingDB('book').books.update({ "seller": bookListing.sellerId, "sellerSku": bookListing.sellerSku },{ $set: {"listingStatus" : "LISTING_CREATED"}})

instead of

printjson(bookListing)

it wll again call book db.

but to test i made thi instead of

printjson

 db.getSiblingDB('book').books.find({ "seller": bookListing.sellerId, "sellerSku": bookListing.sellerSku },{ $set: {"listingStatus" : "LISTING_CREATED"}})

but it doesnot show anyhing

felix · Accepted Answer · 2017-02-10 11:17:11Z

replace printjson(bookListing) by this:

 // set listingStatus bookListing.listingStatus = "someRandomValue"; // save the document. As a document already exist in the collection // with this _id, it will update it. db.books.save(listingStatus);

So your code becomes :

 db.books.find({ "status": "readED", $and: [ { "listingStatus": { $not: { $exists: true } } } ] }).forEach(function(book){ db.getSiblingDB('reading').bookListing.find({"sellerSku": book.sellerSku, "sellerId":book.seller},{"sellerId": 1, "sellerSku": 1}).forEach(function(bookListing){ // set listingStatus bookListing.listingStatus = "someRandomValue"; // save the document. As a document already exist in the collection // with this _id, it will update it. db.books.save(listingStatus); }); });

This will update only matching documents

but i need to add this somerandom value for not all collection. The ones who is not exist and whose sellerid = booklisting seller id
@mark bookListing in this context is the JSON document returned by the query, not a mongodb collection
but that json has columns of booklitsting collection. how can books colletion can save it

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