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Find document from collection where field(column) EXISTS or not in collection in MongoDB >
First, Let's create new collection and insert document in it >
> db.employee.insert({_id : 1, firstName:"ankit"})
> db.employee.insert({_id : 2, firstName:"ankit", salary : 1000 })
> db.employee.insert({_id : 3, firstName:"sam", salary : 2000 })
> db.employee.insert({_id : 4, firstName:"neh", salary : 3000 })
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First line above will create table (or collection) (if table already exists it will insert documents in it).
1) FIND Example > find document from collection where field(column) salary exists >
Now, let's display document of collection where field(column) salary exists >
> db.employee.find({salary:{$exists : true}})
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Output>
{ "_id" : 2, "firstName" : "ankit", "salary" : 1000 }
{ "_id" : 3, "firstName" : "sam", "salary" : 2000 }
{ "_id" : 4, "firstName" : "neh", "salary" : 3000 }
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So, you will see that only newly inserted document which contains column salary was displayed.
2) Now, let's display documents of collection where field salary DOESN'T exists >
> db.employee.find({ salary : {$exists : false}})
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Output>
{ "_id" : 1, "firstName" : "ankit" }
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So, you will see that newly inserted document which contains column salary was NOT displayed.
3) SUMMARY>
So in this mongoDB tutorial we learned how to Find document from collection where field(column) EXISTS or not in collection in MongoDB.
1) FIND Example > find document from collection where field(column) salary exists >
> db.employee.find({salary:{$exists : true}})
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2) Now, let's display documents of collection where field salary DOESN'T exists >
> db.employee.find({ salary : {$exists : false}})
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RELATED LINKS>
What is MongoDB - A quick introduction to database
Labels:
MongoDB
Query MongoDB