Aggregation Operation Examples

In this video we are discussing one example on aggregation operation

So aggregation operation example. In this section we'll see how to use the different aggregate functions

So like your dollar sum, dollar mean, dollar max, etc. So I think for the better idea, let us go for one practical demonstration to show you better

that how this aggregate functions can be used or aggregation functions can be used in

our MongoDB queries. In this demonstration we are discussing about MongoDB aggregation

So at first we're opening one terminal. So control alter T we have opened one terminal

here and in this terminal we'll be doing some query execution and we'll be doing on

the MongoDB database already created that is a my database containing the collection

that is our employee. So at first we're going for pseudo service

mongo db start asking for the password then mongo so we are going for the mongo shell so mongo shell has been obtained so we shall go for show db s so you can find that we are having one database that is the my database so use my database so now going for

db my database is there show so collections so we can go for db employee dot find db employee dot find so this is the respective data we are having

in this database my database and the collection name is employee so let us

execute some queries on it so find the sum of salaries of all employees so how

to execute this one so db. employee dot aggregate then dollar group then colon

we're going for this ID so for this ID you are putting the value null then count

colon we're going for this as dollar sum because we're going for the sum of the

salaries so dollar salary so we have opened three calibrassus so we are closing them and one first bracket

so this is the total case and it should be also a carbure brace so you see db

employee dot aggregate so aggregate is a method and then we are giving this one

as dollar group colon underscore id colon null so in the output couple the ID will be

null and we are going for this count colon that is a sum

salary in this way we're going to get this one so if I press enter I'm

getting this sum of the salary as 16600 that is the sum of the salary so instead of count also we can go for total salary so we getting this one ID is null and total salary is this next one find the age of the youngest employee from the collection so here here you can see that this is the youngest employee means we are going to get this 12 here so this 12 we are expecting so

the query will be db.employee dot aggregate then dollar group is there then underscore id

colon null and then we shall go for this mean edge so there is a key here so we shall go for

dollar mean so instead of sum here will be using this mean and obviously we'll be operating

on edge so you can find that the minimum age is 12 and that we pointed out earlier

okay we're going for the next query the next query is that find the average salary from the employee collection so how to do that one so

here we'll be going for this so id is null there and then we are going for this average

so we're going for this average and then here we'll be going for this avigee and we'll be

operating on salary so in this way we're working So this is the average salary we have got

Okay. Now let us go for the another one Find the average salary of all employees grouped by different cities so if I want to execute this one so find the average salary of all employees grouped by

different cities so dollar group is there so minus colon this is my

underscore ID colon here we can put here dollar city instead of null then you shall go

for this average salary then we are going for this this one and then we shall go for this dollar salary so here you can find that

id here is dollar city so now if i go for enter you are finding this one Kolkata is having the

average salary of 17,000 so let us go for a cross check for Kolkata we are having two salaries

one is the 16 000 another one is the 18000 so the average is 17 000 is quite okay

so let us go for this delisay we're having this 28 500 because for Delhi we're having this 25,000 and for

Delhi we're having this 32,000 so difference is our 7,000 by two so three

thousand five hundred so 28,500 is just the correct one and for London we're

having only one instance of London so it is average salary salary will even the

same that is at 23,000 so in this way we have shown you that how the average

salary of all employees group by different cities can also be calculated so in this demonstration we have shown you that how this

aggregation operations can be done on MongoDB databases thanks for watching this