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$or Operator in MongoDB

$or operator return the value if one expression true from it’s all expression. Its takes any number of expression. $or operator same as like OR operator in SQL Server.
$or operator stop the evaluation if find expression true for it’s all expression. $or operator treat as true to null, 0 and undefined.

Syntax:


{ $or: [ <expression1>, <expression2>, ... ] }


Example: Suppose we have a collection books. Write a query to select books which quantity =1 or price is 20.


{ "_id" : 1, "book_title" : "book1 ","price" : 20, "quantity" : 1, "date" : ISODate("2016-08-05T07:00:00Z") }
{ "_id" : 2, "book_title" : "book2", "price" : 10, "quantity" : 2, "date" : ISODate("2016-08-05T08:00:00Z") }
{ "_id" : 3, "book_title" : "book3", "price" : 30, "quantity" : 4, "date" : ISODate("2016-08-17T10:00:00Z") }
{ "_id" : 4, "book_title" : "book4", "price" : 10, "quantity" : 2, "date" : ISODate("2014-09-01T11:20:39.736Z") }
{ "_id" : 5, "book_title" : "book5", "price" : 20, "quantity" : 6, "date" : ISODate("2014-09-04T20:23:13.331Z") }


Query:


db.books.find({  
     $or:[{"quantity":1},{"price":20}]
 })


Result:


{ "_id" : 1, "book_title" : "book1 ", "price" : 20, "quantity" : 1, "date" : ISODate("2016-08-05T07:00:00.000Z") }
{ "_id" : 5, "book_title" : "book5", "price" : 20, "quantity" : 6, "date" : ISODate("2014-09-04T20:23:13.331Z") }



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