How to use IF ELSE in MongoDB

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Contents of page >

  • 1) First let's create insert documents in collection in MongoDB
  • 2) Write query which prints firstName and salary of employee >
  • If salary >= 2000 then print "high".
  • Else         print "low".


1) First let's create insert documents in collection in MongoDB

1.1) Let's create new collection and insert document in it before finding >
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 })
db.employee.insert({id : 6,  firstName:"neh", salary : 5000 })
Above will create collection (or table) (if collection already exists it will insert documents in it).

1.2) Let’s query all documents of collection using find() method>
> db.employee.find()
Output>
{ "_id" : ObjectId("588205d01e509423fa0faa6d"), "id" : 1, "firstName" : "ank", "salary" : 1000 }
{ "_id" : ObjectId("588205d01e509423fa0faa6e"), "id" : 2, "firstName" : "ank", "salary" : 2000 }
{ "_id" : ObjectId("588205d01e509423fa0faa6f"), "id" : 3, "firstName" : "sag", "salary" : 3000 }
{ "_id" : ObjectId("588205d01e509423fa0faa70"), "id" : 4, "firstName" : "sag", "salary" : 4000 }
{ "_id" : ObjectId("588205d01e509423fa0faa71"), "id" : 5, "firstName" : "neh", "salary" : 5000 }
{ "_id" : ObjectId("588205d01e509423fa0faa72"), "id" : 6, "firstName" : "neh", "salary" : 5000 }


2) Write query which prints firstName and salary of employee >
  • If salary >= 2000 then print "high".
  • Else         print "low".

We will use $cond operator.
db.employee.aggregate(
  [
     {
        $project:
          {
            firstName : 1,
            salaryIsHighOrLow :
              {
                $cond: { if: { $gte: [ "$salary", 2000 ] }, then: "high" , else: "low" }
              }
          }
     }
  ]
)
Output>
{ "_id" : ObjectId("588205d01e509423fa0faa6d"), "firstName" : "ank", "salaryIsHighOrLow" : "low" }
{ "_id" : ObjectId("588205d01e509423fa0faa6e"), "firstName" : "ank", "salaryIsHighOrLow" : "high" }
{ "_id" : ObjectId("588205d01e509423fa0faa6f"), "firstName" : "sag", "salaryIsHighOrLow" : "high" }
{ "_id" : ObjectId("588205d01e509423fa0faa70"), "firstName" : "sag", "salaryIsHighOrLow" : "high" }
{ "_id" : ObjectId("588205d01e509423fa0faa71"), "firstName" : "neh", "salaryIsHighOrLow" : "high" }
{ "_id" : ObjectId("588205d01e509423fa0faa72"), "firstName" : "neh", "salaryIsHighOrLow" : "high" }

In above query >
firstName : 1 > Is used to display firstName field in output.


Summary -
So in this MongoDB tutorial we learned How to use IF ELSE in MongoDB.



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RELATED LINKS>

What is MongoDB - A quick introduction to database


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