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___________ returns either the non-null result of the first expression.

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___________ returns either the non-null result of the first expression.

(a) $Null

(b) $ifNull

(c) $ElseNull

(d) None of the mentioned

I had been asked this question during an interview.

Question is taken from Pipeline Operators topic in chapter Aggregation Concepts and Aggregation Mechanics of MongoDB

1 Answer

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Best answer
The correct choice is (b) $ifNull

Explanation: $ifNull returns the result of the second expression if the first expression results in a null result.

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