Contents of page >
Projections in MongoDB - Selecting specific fields of documents 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) Display only firstName field of document of collection using find() method>
> db.employee.find( {}, {firstName : 1})
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Output>
{ "_id" : 1, "firstName" : "ankit" }
{ "_id" : 2, "firstName" : "ankit" }
{ "_id" : 3, "firstName" : "sam" }
{ "_id" : 4, "firstName" : "neh" }
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By default _id field is always shown.
2) Display only firstName and salary field of document of collection using find() method>
> db.employee.find( {}, {firstName : 1, salary : 1})
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Output>
{ "_id" : 1, "firstName" : "ankit" }
{ "_id" : 2, "firstName" : "ankit", "salary" : 1000 }
{ "_id" : 3, "firstName" : "sam", "salary" : 2000 }
{ "_id" : 4, "firstName" : "neh", "salary" : 3000 }
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By default _id field is always shown.
3) Display only firstName and salary field of document of collection, But avoid _id field to be displayed using find() method>
> db.employee.find( {}, { _id :0, firstName : 1, salary : 1})
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Output>
{ "firstName" : "ankit" }
{ "firstName" : "ankit", "salary" : 1000 }
{ "firstName" : "sam", "salary" : 2000 }
{ "firstName" : "neh", "salary" : 3000 }
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4) FIND Example > Display only firstName and salary field of document of collection where salary > 1000, But avoid _id field to be displayed using find() method>
> db.employee.find( { salary : {$gt : 1000} }, { _id :0, firstName : 1, salary : 1})
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Output>
{ "firstName" : "sam", "salary" : 2000 }
{ "firstName" : "neh", "salary" : 3000 }
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5) SUMMARY>
So in this mongoDB tutorial we learned about Projections in MongoDB - Selecting specific fields of documents in collection in MongoDB.
Display only firstName field of document of collection using find() method>
> db.employee.find( {}, {firstName : 1})
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Display only firstName and salary field of document of collection using find() method>
> db.employee.find( {}, {firstName : 1, salary : 1})
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Display only firstName and salary field of document of collection, But avoid _id field to be displayed using find() method>
> db.employee.find( {}, { _id :0, firstName : 1, salary : 1})
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RELATED LINKS>
What is MongoDB - A quick introduction to database
Labels:
MongoDB
Query MongoDB