SQL

Suppose there is an SQL table of messages. messages: id, sender_id, receiver_id, message How would you find the set of unique communicators from that?

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Interview question asked to Data Scientists interviewing at Airbnb, Grubhub, Roku and others: Suppose there is an SQL table of messages. messages: id, sender_id, receiver_id, message How would you find the set of unique communicators from that?.