Contents of page >
- Step 2.1 - We will group employee by firstName and find minimum salary of each group.
- Step 2.2- We will use aggregate() method, $min operator and $group operator.
- 2.3) Sql query equivalent to above MongoDB query is >
- Step 3.1 - We will group employee by null (nothing) and find minimum salary of group (there will be only 1 group - i.e. whole documents of collection)
- Step 3.2- We will use aggregate() method, $min operator $group operator.
- 3.3) Sql query equivalent to above MongoDB query is >
- Find minimum salary of all employee with same firstName where salary > 2000 in collection in MongoDB >
- Step 4.1 - We will find document where salary > 2000
- Step 4.2 - We will use $match operator
- Step 4.3 - Then we will group employee by firstName and find minimum salary of each group.
- Step 4.4 - We will use aggregate() method, $group operator, $min operator and _id : null
- 4.5) Sql query equivalent to above MongoDB query is >
$min operator in MongoDB >
$min operator returns the minimum value from documents in the collection in MongoDB.
1) First let's create insert documents in collection in MongoDB
1.1) First, Let's create new collection and insert document >
db.employee.insert({_id : 1, firstName:"ank", salary : 1000 })
db.employee.insert({_id : 2, firstName:"ank", salary : 2000 })
db.employee.insert({_id : 3, firstName:"sag", salary : 3000 })
db.employee.insert({_id : 4, firstName:"sag", salary : 4000 })
db.employee.insert({_id : 5, firstName:"neh", salary : 5000 })
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Above will create collection (or table) (if collection already exists it will insert documents in it).
1.2) FIND > Query all documents of collection using find() method>
db.employee.find()
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Output>
{ "_id" : 1, "firstName" : "ank", "salary" : 1000 }
{ "_id" : 2, "firstName" : "ank", "salary" : 2000 }
{ "_id" : 3, "firstName" : "sag", "salary" : 3000 }
{ "_id" : 4, "firstName" : "sag", "salary" : 4000 }
{ "_id" : 5, "firstName" : "neh", "salary" : 5000 }
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2) Find minimum salary of employee with same firstName in collection in MongoDB >
Step 2.1 - We will group employee by firstName and find minimum salary of each group.
Step 2.2- We will use aggregate() method, $min operator and $group operator.
> db.employee.aggregate([{$group : {_id : "$firstName", salary_minimum : {$min : "$salary"}}}])
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Output >
{ "_id" : "ank", "salary_minimum" : 1000 }
{ "_id" : "sag", "salary_minimum" : 3000 }
{ "_id" : "neh", "salary_minimum" : 5000 }
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2.3) Sql query equivalent to above MongoDB query is >
select firstName, min(salary) salary_minimum from employee group by firstName;
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3) Find minimum salary of all employee in collection in MongoDB >
Step 3.1 - We will group employee by null (nothing) and find minimum salary of group (there will be only 1 group - i.e. whole documents of collection)
Step 3.2- We will use aggregate() method, $min operator $group operator.
> db.employee.aggregate([{$group : {_id : null, salary_minimum : {$min : "$salary"}}}])
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Output >
{ "_id" : null, "salary_minimum" : 1000 }
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3.3) Sql query equivalent to above MongoDB query is >
select min(salary) salary_minimum from employee;
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4) How to write aggregate query with where clause in MongoDB >
Find minimum salary of all employee with same firstName where salary > 2000 in collection in MongoDB >
Step 4.1 - We will find document where salary > 2000
Step 4.2 - We will use $match operator
Step 4.3 - Then we will group employee by firstName and find minimum salary of each group.
Step 4.4 - We will use aggregate() method, $group operator, $min operator and _id : null
> db.employee.aggregate([
{ $match: { salary : { $gt: 2000} } },
{$group : {_id : "$firstName", salary_minimum: {$min : "$salary"}}}])
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Output >
{ "_id" : "sag", "salary_minimum" : 3000 }
{ "_id" : "neh", "salary_minimum" : 5000 }
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4.5) Sql query equivalent to above MongoDB query is >
select firstName, min(salary) salary_minimum from employee
where salary > 2000
group by firstName
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5) Summary -
So in this MongoDB tutorial we learned about $min operator in MongoDB. $min operator returns the minimum value from documents in the collection in MongoDB.
Find minimum salary of employee with same firstName in collection in MongoDB >
> db.employee.aggregate([{$group : {_id : "$firstName", salary_minimum : {$min : "$salary"}}}])
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Find minimum salary of all employee in collection in MongoDB >
> db.employee.aggregate([{$group : {_id : null, salary_minimum : {$min : "$salary"}}}])
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Find minimum salary of all employee with same firstName where salary > 2000 in collection in MongoDB >
> db.employee.aggregate([
{ $match: { salary : { $gt: 2000} } },
{$group : {_id : "$firstName", salary_minimum: {$min : "$salary"}}}])
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