Question

I have a query below that I use to retrieve the records not updated for a given time (in hours) and order it by elapsed time:

SELECT TABLE.Key, TIMESTAMPDIFF(HOUR, TABLE.Date_last_consulted, CURRENT_TIMESTAMP)
FROM TABLE WHERE TIMESTAMPDIFF(HOUR, TABLE.Date_last_consulted,
CURRENT_TIMESTAMP) <= 7 ORDER BY TIMESTAMPDIFF(HOUR, TABLE.Date_last_consulted,
CURRENT_TIMESTAMP);

As you can see, it calls multiple times TIMESTAMPDIFF, which is not very efficient as all these calls lead to useless SQL calculations.

I was wondering if there were a way to reuse the calculations so it is processed only once?

Thanks a lot for your help.

Florent

Answer 1

SELECT 
    t.Key, t.dif
FROM (
        SELECT key, TIMESTAMPDIFF(HOUR, TABLE.Date_last_consulted, CURRENT_TIMESTAMP) dif
        FROM TABLE
     ) t
WHERE 
    t.dif <= 7 
ORDER BY 
    t.dif