Question

suppose I have a table which has a column days(‘mon’,’tue’,’wed’,’thu’,’fri’), how do I implement a days-of-week order (rather than lexicographical order) to them?

eg.

'mon'<'tue' //produce true

'fri'>'wed' //true

'fri'<'thu' //false

Thanks in advance!

Answer 1

Not the way you want:

ORDER BY CASE day
    WHEN 'mon' THEN 1
    WHEN 'tue' THEN 2
    ...
    WHEN 'sun' THEN 7
END

Edit: you can also create a second table:

day_name day_order
======== =========
mon              1
tue              2
...
sun              7

… and JOIN and SORT when SELECTing.

Last but not least, store days as numbers 🙂