CURD
  ___________


  Insert
  -------------------------







db.users.insertOne({
  name: "John Doe",
  email: "john.doe@example.com",
  age: 30
})


db.users.insertMany([
  { name: "Alice", email: "alice@example.com", age: 25 },
  { name: "Bob", email: "bob@example.com", age: 28 }
])



Monfo db _id automatically har doccument ko deta hai 

db.users.insertOne({ _id: 1, name: "David", email: "david@example.com" })
If you attempt to insert a document with a duplicate _id, MongoDB will throw an error:

E11000 duplicate key error collectiondb.users.insertOne({ _id: 1, name: "David", email: "david@example.com" })
If you attempt to insert a document with a duplicate _id, MongoDB will throw an error:

E11000 duplicate key error collection


agar koi csv file hai to wahah is ek bhi bar me insetmany ka istmmal karke data insert kar sakte hai




___________________________________________________________________________


 Read
 -----------






Find Without Criteria
db.users.find()  ---- sabi document ko read karega


Find With Criteria
db.users.find({ name: "Alice" })

Projection ka matlab hota hai sirf selected fields dikhana.
db.users.find({}, { name: 1, _id: 0 })
👉 Isme:

name: 1 → sirf name show karo

_id: 0 → _id hide karo

📌 Result: sirf users ke names dikhenge.


✅ 2. Using Operators

Operators filtering ke liye use hote hain:

$gt → greater than (>)

$lt → less than (<)

$eq → equal

$ne → not equal


db.users.find({ age: { $gt: 25 } })
👉 Matlab: jin users ki age 25 se zyada ho, sirf wahi lao.


agar keval one document chaye

db.users.findOne({ name: "Bob" })




db.users.find().sort({ age: 1 }).limit(5)

1. Sort — Order lagana
.sort({ age: 1 })


👉 age: 1 ka matlab:
age ko ascending order (choti se badi) me arrange karo.

📌 Agar -1 hota:

.sort({ age: -1 })

2. Limit — Result kam karna
.limit(5)


👉 Sirf first 5 documents return honge.
Top 5 youngest users


________________________________________________________




  Update
  --------------


  db.users.updateOne({ name: "Alice" }, {
  $set: { age: 26 }
})


db.users.updateMany({ age: { $lt: 30 } }, {
  $set: { status: "active" }
})


The $inc operator is used to increment or decrement
numeric values. For example:

db.users.updateOne({ name: "Alice" }, {
  $inc: { age: 1 }
})

db.users.updateOne({ name: "Alice" }, {
  $set: { age: 26 }
})
🧠 Agar 5 documents me name: "Alice" match ho jaayein — to kya hoga?
👉 Sirf PEHLA matching document update hoga.




Adding a New Attribute

If the specified attribute does not exist, MongoDB will
add it to the document. For example:

db.users.updateOne({ name: "Bob" }, { $set:
{ city: "New York" } })

Removing an Attribute

Use the $unset operator to remove an attribute from a
document. For example:

db.users.updateOne({ name: "Alice" }, {
  $unset: { city: "" }
})



______________________________________________________________________________



   Delete
   ----------



   deleteOne

This method deletes a single document that matches the
given criteria. For example:

db.users.deleteOne({ name: "Alice" })

deleteMany

This method deletes multiple documents that match the
specified criteria. For example:

db.users.deleteMany({ age: { $lt: 30 } })

Deleting All Documents

To delete all documents within a collection, you can use:

db.users.deleteMany({})