MongoDB - How to Update Documents in MongoDB using Robo 3T

MongoDB provides the update() command to update the documents of a collection. To update only the documents you want to update, you can add a criteria to the update statement so that only selected documents are updated.

db.collection.update(query, update, options)

By default, the db.collection.update() method updates a single document. To update multiple documents, use the multi option.

Syntax: db.collection.update(    <query>,    <update>,    {      upsert: <boolean>,      multi: <boolean>,      writeConcern: <document>,      collation: <document>,      arrayFilters: [ <filterdocument1>, ... ],      hint:  <document|string>        // Available starting in MongoDB 4.2    } )

The db.collection.update() method takes the following parameters:

Parameter	Type	Description
Query	Document	The selection criteria for the update. The same query selectors as in the find() method are available.
Update	Document or pipeline	The modifications to apply.
Option
Upsert	Boolean	Optional. If set to true, creates a new document when no document matches the query criteria. The default value is false, which does not insert a new document when no match is found.
multi	Boolean	Optional. If set to true, updates multiple documents that meet the query criteria. If set to false, updates one document. The default value is false.
wrireConcern	Document	Optional. A document expressing the write concern. Omit to use the default write concern w: 1.
Collation	Document	Optional: Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks.
arrayFilters	Array	Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks.
Hint	Document or string	Optional. A document or string that specifies the index to use to support the query predicate.

Let take an example to update the document or documents using update method. Side by side we can also check the RDBMS syntax to better understanding.

First check the how many documents we have in an inventory collection in TechDB database.

Example - 1 Update the document where item = “mat” and set the new value of qty = 100 and size.h=30 Lets first find the document where item = “mat”. We found 1 document only.

MongoDB Update method	RDBMS syntax
db.inventory.update(     {"item":"mat"},     {$set:         {"qty":100,"size.h":30}     } )	Update inventory Set qty = 100, h=30 Where item = “mat”
Explanation: {“item”:”mat”} -- query parameter Update parameter and $set is update operator. {$set:         {"qty":100,"size.h":30} } Option parameter is optional	Where item = “mat” -- Filter criteria
Let's check the document updated or not. db.inventory.find({item:"mat"})
You can see above document updated successfully. qty = 100 and size.h = 30.0
Example - 2 Let's update the document or documents where status = “A” and set the new value of qty = 10 first find the document where status = “A”. We found 6 documents in inventory collection.
MongoDB Update method	RDBMS syntax
db.inventory.update(     {"status":"A"},     {$set:         {"qty":10}     } )	Update inventory Set qty = 10 Where status = “A”
Only 1 document updated	All records updated
Lets view the documents again where status = “A”
You can see only 1 document updated with qty = 10. This happened because by Default Update() method updates a single document . To update multiple documents, use the multi option in option parameter. Lets run the same update statement with multi = true
Syntax: db.inventory.update(     {"status":"A"},     {$set:         {"qty":10}     },     {       Multi : true     } )
Lets check the documents updated or not in inventory collection.
db.inventory.find({status:"A"})
Now all the documents updated with qty = 10.

Example - 3 Update the document where item = “canvas”. I have added few elements / fields in this documents to understand the update.
Let check first what and how the document looks like before update. We have only one document that meet the search criteria where item = “canvas”
In this document we have  Size have 3 fields "size" : { "h" : 28.0, "w" : 35.5, "uom" : "cm"} Color have 2 elements “color” : [“red”,”black”] Ratings have 2 elements and each element have 2 fields. In this example we are going to update 2nd element (highlighted). "ratings" : [ {"by" : "abc","rating" : 2}, {"by" : "xyz","rating" : 4} ]
Now we are going to update these fields and elements. db.inventory.update(    { item : "canvas" },    {      $inc: { qty: 125 },      $set: {        "size.h": 31,        "color": [ "brown" ],        "ratings.1": { "by": "sk", "rating": 5 }      }    } )
The result should be
Before Update	After Update	Description
Qty = 10	Qty = 10+125 = 135	$inc operator increments a field by a specified value
Size.h = 28.0	Size.h = 31.0	Size.h means update only “h” Update the size.h value by $set operator
Color = red, black	Color = brown	Update the array element by $set operator
Ratings.1 by = “xyz” and /n rating=4	Ratings.1 by = “sk” and rating=5	Ratings.1 means 2nd element and Ratings.0 means 1st element. Update the fields of an array element by $set operator
Now check the documents updated or not.
You can see all the fields of Document updated successfully.