MongoDB Tutorial for Beginners 13 - MongoDB Aggregation Video Lecture | The Complete Developers Guide to Mongo DB - Database Management

hello guys welcome to the next video on
MongoDB database tutorial for beginners
in this video we will learn about
aggregation in MongoDB so first of all
what is aggregation aggregation
operation groups values from multiple
documents together and can perform a
variety of operations on the grouped
data and it's going to return a single
result after the aggregation now if you
have used SQL relational databases if
you know when you have whenever you give
the query for example select count and
in the bracket Astrix this count is for
aggregation and this count will return
you who the number of rows right in the
same way the aggregation function works
in MongoDB now how we can perform this
aggregation in MongoDB let's see so I'm
going to use you know Windows command
prompt for this video so I'm going to
switch to Mongo and then press Enter and
in here I will switch to my students
collection in the school database so I
will just write use school and yes
switch to school and first of all let's
see what data we have in the school so
I'm going to just write DB dot students
dot find and let's print this and we
have this much amount of document inside
our database right and if you notice I
have added this gender field also to the
documents if the student is male or
female
right now to perform aggregation what
you need to do is we need to just write
DP then dot the collection name for
example students something like this and
then
use the command called aggragate and
inside these round bracket gave first of
all these square brackets and then once
again the the curly brackets and inside
the curly brackets first of all we will
give the aggregate operation so what can
be our aggregate operation for example
we want to group the student on the
basis of male and female so we want to
count how many female students we have
and how many male students we have so we
can just write dollar group here and
then give a colon and once again give
these curly brackets and here in these
curly brackets we will give the
condition on the basis of which we want
to group the students so we want to
group on the basis of ID and what we
want to group we want to group gender so
just in the double course just write
dollar this is important just write
dollar and then gender which is the name
of your field right so just write gender
which is same as this field in your JSON
document you can see here right and then
once we have given that we need to
specify the format of result so after
comma the next argument will be the
result and here the first keyword you
can define on yourself so for example
you can just say my result or something
like this you whatever word or keyword
you want to see in the answer you can
just give that word and then colon and
then once again curly brackets and
inside the curly bracket what we want to
do what operation we want to perform
here we can perform some minimum maximum
average and other operations
here so we are going to perform some for
now so just write dollar sum and then
just give call : and then give here true
or one right and then we are going to
perform this command so press ENTER and
it returns us mail number of mail we
have three males and three females in
our documents right now for example we
want to find the maximum and minimum age
of students inside our documents how we
can do it so in here we will pass the
same query but instead of my result for
example we can say max age for the
result and then instead of using some we
can use max here so just write max and
instead of true we can pass the field
which we want to perform the operation
on so for example we want to perform
this operation on age you want to find
the maximum age right so just give in
double quotes this age field and then
press enter and it returns us error
because I think I forget to give the
taller symbol before age so just give
dollar age
don't forget the dollar symbol here and
press enter once again and you can see
here the maximum age for male is 40 here
and maximum age for a female is 17 here
right and similarly we can do the
minimum age operation so min age and
here you just need to write min and
press enter and once again it gives us
error because instead of type in min I
typed mix so just once again we will
correct this operation min and then
press Enter and it returns us
minimum age of male is 13 and minimum
age or female is 12 here okay so in this
way you can perform aggregation in
MongoDB I hope you've enjoyed this video
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now