If you want to create a new field with conditional logic (like IF-ELSE) in aggregation, which operator would you use?

Which of the following ensures that a distributed database system maintains ACID properties across multiple sites?

When a new attribute is added to a relation during schema evolution, the usual way to handle existing tuples is to Assign a value or null to the new attribute

The stage in the aggregation pipeline is used to combine documents and apply accumulators like $sum, $avg, $max

A good key design in key-value databases should ensure:

If a client reads a value and then later reads again, Consistency guarantees , the second read will never return an older value

Which MongoDB command is used to retrieve documents from a collection ?

In MongoDB aggregation, combining $match before $group is often done because:

Lack of support for complex queries and relationships  is a common of key-value databases

Which of the following real-world databases is an example of a CP (Consistency + Partition Tolerance) system?