Explanation:$ifNull returns the result of the second expression if the first expression results in a null result. 10.__________ take as input a single expression, evaluating the expression once for each input document, and maintain their state for the group of documents.
A. Computer
B. Monitors
C. Accumulators
D. Performoner
Answer:A
Explanation:$ifNull returns the result of the second expression if the first expression results in a null result. 10.__________ take as input a single expression, evaluating the expression once for each input document, and maintain their state for the group of documents.
A. Computer B. Monitors C. Accumulators D. Performoner
Explanation:Accumulators are available only for the $group stage. Sanfoundry Global Education & Learning Series – MongoDB.