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?

Question

Anonymous · Accepted Answer

unique communicators = anybody who receives or sends msgs

SELECT DISTINCT sender_id as user_id

FROM messages

UNION

SELECT DISTINCT receiver_id as user_id

FROM messages

unique communicators = unique pairs

SELECT DISTINCT

LEAST(sender_id, received_id) AS user1,

GREATEST(sender_id, receiver_id) AS user 2

FROM messages

Anonymous · Answer

Assuming communicator is part of the sender_id and reciever_id:

SELECT sender_id AS user_id

FROM messages

UNION

SELECT receiver_id AS user_id

FROM messages;

Anonymous · Answer

SELECT DISTINCT sender_id FROM TABLE. This is a simple sql question to extract
the distinct senders (communicator). This also disregards the number of messages
sent per senders

Anonymous · Answer

to find the set of unique communicators, this is the SQL query

select distinct id, sendor_id, receiver_id, message from messages

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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