Introduction to mongoDB database

In MongoDB

Collection    :   Table
Document    :   Row
Field            :   Column

1. Find all documents of items collection

1. db.items.find();

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2. Find documents of items collection whose price is 10

db.items.find({ price : 10 });

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3. Find documents of items collection whose price is greater than 20

db.items.find( { price : { $gt : 20 } });

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4. Find documents of items collection whose price is greater than 20 and less than 100

db.items.find({ price : { $gt : 20, $lt : 100 } });

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5. Loop through all documents of items collection and print JSON

	var myCursor = db.items.find();
	myCursor.forEach(printjson);

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6. Find first two document of items collection

db.items.find().limit(2);

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7. Skip first two document of items collection and display others

db.items.find().skip(2);

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8. Insert a document in items collection

	db.items.insert({
	name : 'daal makhni',
	itemCode : 'a1',
	price : "120",
	sellingPrice : "140",
	restaurant : "5540ca56d1f925f156a8c33d"
	});

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9. Find first document of items collection
db.items.findOne(); is same as db.items.find().limit(1);

db.items.findOne();

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10. Find all document of items collection where name is ‘daal’ or ‘daal makhni’

db.items.find({ name : { $in : ['daal', 'daal makhni'] } });

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11. And condition

	db.items.find({ name : 'daal', price : 10});
	db.items.find({ $and : [{ name : 'daal', price : 10}] });
	db.items.find({ $and : [ {name : 'daal'}, {price : 10} ] });

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12. Or condition

db.items.find({ $or : [{name : 'daal'}, {price : 20}] });

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13. $and and $or both condition

db.items.find({ type : 'veg', $or : [ { name : 'daal'}, {name : 'rice'} ] });

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14. Start mongoDB shell
      This will connect you to running mongod instance

mongo (Enter this in terminal)

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15. Show the list of databases

show dbs

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16. Show current db

db

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17. If database nite-foodie-internal is exist then this command switch to nite-foodie-internal database. If database nite-foodie-internal is not exist then this command create database named nite-foodie-internal

use nite-foodie-internal

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18. Deleted all collection of current database

db.dropDatabase();

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19. Show all collections of current database

show collections

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20. Create collection items in current database

db.createCollection(‘items’);

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21. Delete collection items of current database

db.items.drop();

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22. Update query
      Update the title

	db.COLLECTION_NAME.update(SELECTIOIN_CRITERIA, UPDATED_DATA);
	db.items.update({ title : 'first title'}, { $set : { 'title' : 'new title' } });

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23. Delete documents where title equal to ‘new title’ of items collection

db.items.remove({title : 'new title'});

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24. Delete all documents of items collection

db.items.remove({});

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25. Find all documents of items collection and display only name price and type of each document.
In MongoDB when you execute find() method, then it displays all fields of a document. To limit this you need to set list of fields with value 1 or 0. 1 is used to show the field while 0 is used to hide the field.

db.items.find({}, {name:1, price:1,type:1});

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26. Sort is used to sort data
      1 is used for ascending order while -1 is used for descending order

	db.items.find({}).sort({ 'name' : 1});
	db.items.find({}).sort({ 'name' : -1});

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27. This query will loop through all documents of collection items and sum all price of same type
{ "_id" : "egg", "total_price" : 30 }
{ "_id" : "non-veg", "total_price" : 20 }
{ "_id" : "veg", "total_price" : 161 }

db.items.aggregate([ { $group : { _id : "$type", total_price : { $sum :"$price" } } } ]);

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28. Create backup

	mongodump --collection COLLECTION_NAME --db DB_NAME
	mongodump --db nite-foodie-internal
	// create backup of nite-foodie-internal database
	mongodump --collection items --db nite-foodie-internal
	// create backup of items collection of nite-foodie-internal database

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29. Restore database nite-foodie-internal to mongoDB

mongorestore dump/nite-foodie-internal

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30. Returns the count of documents that would match a find() query

db.items.find({}).count();

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31. Apply regex in mongoDB query

db.items.find({ cuisine : new RegExp('^Indian$', 'i') });

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32. How to export MongoDB database in CSV format

	mongoexport --host localhost --db databaseName --collection collectionName --csv --out fileName.csv --fields commaSeperatedFieldsName
	mongoexport --host localhost --db nite-foodie-pro --collection customers --csv --out text.csv --fields number

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