Question

Which of the following returns a substring of a string?

(a) $subs

(b) $substring

(c) $substr

(d) None of the mentioned

This question was addressed to me at a job interview.

Origin of the question is Pipeline and Sharded Collections in section Aggregation Concepts and Aggregation Mechanics of MongoDB

Answer 1

Right option is (c) $substr

For explanation: $substr accepts three expressions as arguments: the first argument must resolve to a string, and the second and third arguments must resolve to integers.