show dbs;
use students;
//DOCUMENTS:
//{ "_id" : ObjectId("65425ee24dae169ba3f964c1"), "name" : "GANESH", "age" : 20 }
//{ "_id" : ObjectId("654291025dbfaef1293ed2a1"), "name" : "adi", "age" : 21 }
//{ "_id" : ObjectId("654292245dbfaef1293ed2a2"), "name" : "pawan", "age" : 23 }
//{ "_id" : ObjectId("654292245dbfaef1293ed2a3"), "name" : "om", "age" : 21 }
//{ "_id" : ObjectId("654292245dbfaef1293ed2a4"), "name" : "adi", "age" : 21 }
//CRUD OPERATIONS
1)C : CREATE and INSERT
db.createCollection("students");
show collections;
db.students.insert({"name":"GANESH","age":21});
db.students.find();
2)R : READ
db.students.find({name:"pawan"}); == db.students.find({query})
//Output-->{ "_id" : ObjectId("654292245dbfaef1293ed2a2"), "name" : "pawan", "age" : 23 } //Whole document having name:"pawan"
db.students.find({name:"pawan"},{name:1/0}); == db.students.find({query},{projection})
//Output--> { "_id" : ObjectId("654292245dbfaef1293ed2a2"), "name" : "pawan" } //With "_id"
db.students.find({name:"pawan"},{_id:0,name:1});
//Output-->{ "name" : "pawan" }
db.students.find({age:21}).limit(1); //Returns only one document amongs multiple documents
//Output-->{ "_id" : ObjectId("65425ee24dae169ba3f964c1"), "name" : "GANESH", "age" : 21 }
//another method for same :db.students.findOne({age:21});
db.students.find({age:21}).limit(1).skip(1);//To skip first record
//{ "_id" : ObjectId("654291025dbfaef1293ed2a1"), "name" : "adi", "age" : 21 } //first record = GANESH is skipped
3) U : UPDATE
db.students.update({name:"adi"},{$set:{age:25}}); //AGE of adi becomes 21 to 25
//Output-->{ "_id" : ObjectId("654291025dbfaef1293ed2a1"), "name" : "adi", "age" : 25 }
4) D : DELETE
db.students.remove({name:"GANESH"}); //to delete single document
//Output-->{ "_id" : ObjectId("654291025dbfaef1293ed2a1"), "name" : "yogesh", "age" : 25 }
//{ "_id" : ObjectId("654292245dbfaef1293ed2a2"), "name" : "pawan", "age" : 23 }
//{ "_id" : ObjectId("654292245dbfaef1293ed2a3"), "name" : "om", "age" : 21 }
//{ "_id" : ObjectId("654292245dbfaef1293ed2a4"), "name" : "adi", "age" : 21 }
db.students.drop();//to delete whole collection
//Output-->true
//GANESH
