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MongoDB

C100DBA · Question #37

Which of the following operator can be used to control the number of items of an array that a query returns?

The correct answer is B. $slice. $slice is the correct projection operator for controlling how many elements MongoDB returns from an array field. You can use it to return the first N elements ($slice: N), the last N elements ($slice: -N), or a range ($slice: [skip, limit]) - making it ideal for paginating or tri

MongoDB Fundamentals

Question

Which of the following operator can be used to control the number of items of an array that a query returns?

Options

  • A$ elemMatch
  • B$slice
  • C$
  • DMongoDB does not support partial retrieval of items from an array

How the community answered

(44 responses)
  • A
    5% (2)
  • B
    93% (41)
  • D
    2% (1)

Explanation

$slice is the correct projection operator for controlling how many elements MongoDB returns from an array field. You can use it to return the first N elements ($slice: N), the last N elements ($slice: -N), or a range ($slice: [skip, limit]) - making it ideal for paginating or trimming array results without fetching the full array.

Why the others are wrong:

  • $elemMatch filters which elements are returned based on a condition, but it only returns the first matching element - it doesn't control count.
  • $ (positional operator) also returns only the first array element that matches the query condition; it's about targeting, not quantity control.
  • D is false - MongoDB fully supports partial array retrieval through projection operators.

Memory tip: Think of $slice like JavaScript's Array.prototype.slice() - same name, same idea: carve out a portion of an array by position and length.

Topics

#$slice#array projection#cursor operators#query operators

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