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POprovide extra return column of boolean type which evaluates another query
 

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  1. POprovide extra return column of boolean type which evaluates another query
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    <p>I am trying to develop a query that will </p> <ol> <li>Give the last message in every thread that was not written by the currentUserID (right now accomplished with group by thread_id, order by message_id desc AND WHERE results.sender_id != currentUserID)</li> <li>If the user started a thread but received no response then the thread should not show up (right now accomplished by simply filtering the data with WHERE results.sender_id != currentUserID)</li> <li>Provide a boolean column to tell if a response was sent in this thread (not accomplished but would involve finding the last element from the query and seeing if the sender_id is = to current logged in user id)</li> </ol> <p><a href="http://sqlfiddle.com/#!2/85971/2" rel="nofollow">http://sqlfiddle.com/#!2/85971/2</a></p> <p><strong>Synopsis</strong></p> <ul> <li>User 1 sends a message with User 2 with</li> <li>Thread ID: 1</li> <li>Subject: 'Hi Subject'</li> <li><p>Body: 'Hi Body'</p></li> <li><p>User 2 responds:</p></li> <li>Thread ID: 1</li> <li>Body: 'Hi Body Response'</li> </ul> <p><strong>As User 1 the SQL Should Return</strong></p> <pre><code>THREAD_ID |SUBJECT | SENDER_ID | BODY | Responded 1 | Hi Subject | 2 | Hi Body Response | false </code></pre> <p><strong>As User 2 the SQL Should Return</strong></p> <pre><code>THREAD_ID |SUBJECT | SENDER_ID | BODY | Responded 1 | Hi Subject | 1 | Hi Body | true </code></pre> <p>Please see fiddle</p> <p>My shot at it was the following which takes acre of 1 and 2 but not 3, I tried to mess around with UNIONS to achieve this but got nowhere.</p> <pre><code>SELECT * FROM ( SELECT t.id as thread_id, t.subject, m.sender_id, m.body FROM messages m JOIN threads t ON (m.thread_id = t.id) ORDER BY t.id asc, m.cdate desc ) as results WHERE results.sender_id != currentUserID GROUP BY results.thread_id; </code></pre>
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