5. MongoDB : Work with (Database, Collection and Documents)

5. MongoDB : Work with (Database, Collection and Documents)

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db.createCollection(...)
db.items.insert(...);       //{....}
db.items.find(...);         // {....}, $lt, $lte, $gte, $in, $or, /...,  $slice,  $elemMatch, 
db.items.update(...)      // {....}. $set
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show dbs;     //show all existing db's
use test;        //to switch to test db, if test does not exist then it creates and then switch

show collections;

db.createCollection("items");

//insert  ####################################################

db.items.insert({"name":"Sumit","courses":["mongodb","AWS","GCP"]});  //create document inside collection

db.items.find();

db.items.find({"name":"Sumit"});

db.items.find({"name":"Sumit"}).pretty();

//Bulk insert, if we dont give _id -> then it mongodb takes some unique id

var bulk = db.items.initializeOrderedBulkOp();

bulk.insert({_id:1, item:"pen", available:true, soldQty:700});

bulk.insert({_id:2, item:"pencil", available:false, soldQty:900});

bulk.insert({_id:3, item:"books", available:true, soldQty:700});

bulk.execute();

var bulk = db.items.initializeUnorderedBulkOp();

bulk.insert({_id:4, item:"pen", available:true, soldQty:700});

bulk.insert({_id:5, item:"pencil", available:false, soldQty:900});

bulk.insert({_id:6, item:"books", available:true, soldQty:700});

bulk.execute();

db.items.find();

db.items.find({available:true}).limit(5);  //limit(5) = row=5

db.items.findOne();

db.items.findOne({available:true});

db.items.find({available:true}).pretty();

db.items.find({soldQty: {$lt:800}});     //lessthan 800

db.items.find({soldQty: {$lte:800}, available:true});  //lessthan or equal to

db.items.find({available:{$in:[true,false]}});  //IN

db.items.find({available:true,soldQty:{$lt:900}}); //AND or ,

db.items.find({ $or: [{available:true},{soldQty:700}] }); //OR condition, note: within that mention in {},{}

//regular expression  ####################################################

//regular expression match, eg: in website search_______ anything in website

db.items.find({item:/pe/i});   //caseinsensitive //search anything which has 'pe' or 'i' in it

db.items.find({item:/Pen?/i}); //caseinsensitive //search anything which has 'pe' or 'i' in it

//array serch  ####################################################

db.itesm.find({country_codes:5});  //if country_codes is array - then search for '5' inside that.

db.itesm.find({country_codes.0:5});

//projection quries. (Only for Arrays : $elemMatch, $slice)

//here country_codes is array.

db.items.find({_id:5},{country_codes:{$slice:2}}); //shows only 1st 2 array elements, 

note: if you give {$slice:-2} then it shows last 2 elements of array.

db.itesm.find({country_codes:{$elemMatch:{$gte:3,$lte:6}}}); //between 3 and 6, inside an array elemMatch

//javascript inside query ####################################################

//javascript inside query - using "$where"

db.items.find({"$where":function().......});

db.items.find(({"$where": "this.x + this.y == 10"});

db.items.find(({"$where": "function() {return this.x + this.y == 10;}"});

//cursor, ####################################################

//cursor, light way of handling on dataset query.

var cursor = db.collection.find();

while(cursor.hasNext()) {

....obj= cursor.next();

.....

}

db.c.find.skip(3);

db.c.find().soft({username:1,age:-1})

//UPDATE RECORD ####################################################

//update document where item=Book
//Note: below taken is different example of "items" collection.

db.items.update({item:"Book"},{$set: {category: 'NoSQL', details: {ISDN: "1234", publisher:"XYZ"}}});

//update an embedded field
db.items.update({item: "Pen"},{$set: {"details.model":"14Q2"}});

//update multiple documents. (multi:true)
db.items.update({item: "Pen"},{$set:{catogory:"stationary"},$currentDate:{lastModified:true}},{multi:true});