CRUD Operations using MongoDB

      CRUD Operations Cheat Sheet

 Let us understand how can we perform CRUD operations in MongoDB.

• CRUD stands for Create, Read, Update and Delete
• We can create documents using the InsertOne function.

                              db.inventory.insertOne(

                                  { “item” : “canvas”,

                                     “qty” : 100,

                                     “tags” : [“cotton”],

                                     “size” : { “h” : 28, “w” : 35.5, “uom” : “cm” }

                                 }

                                 )

• find or findOne can be used the documents from the collection, while find returns all the documents matching condition,findOne returns only first document

                             myCursor = db.inventory.find( { status: “D” } )

• Update function can be used to update an existing document , if we set upsert as true then the documents will be inserted if it does not exist.

• We can only perform operations such as $min, $max, $inc, $set etc as part of update. It is not possible to derive data from existing fields and update by using functions such as lower, upper, etc.

• Following are the functions which can be used to update.  
• update(same as updateOne)
• updateMany(updates multiple documents)

                                 db.inventory.updateMany(

• updateOne

                                        db.inventory.updateOne(

• Data can be deleted  using functions such as deleteMany, deleteOne ,findOneAndDelete.
• The following operation deletes the first document with status equal to D:

                              db.inventory.deleteOne(