ORDER BY based on multiple WHERE cases, is this possible? - mysql

Question

Events can be a 1 day event or be an on-going event. This means that sometimes events can go for multiple days, weeks, or months.
As it is now, it is possible to sort the query result by END in ascending order (those expiring earlier shows first) or START in ASC (events based on start date). However, in both cases I have limitations that I am trying to reduce as much as I can.
When sorting by END, sometimes events that are ongoing and have already started get pushed to later in the list.
When sorting by START, events that have already started and are ongoing end up taking up the first sections of the list.
Is it possible to chain multiple ORDER BY statements based on logic rather than columns?
For example:
Get events that are expiring within the next 7 days:
SELECT * FROM data WHERE end < NOW() + INTERVAL 7 DAY;
Get events that are still ongoing between 7 days from today and ending within 14 days:
SELECT * FROM data WHERE NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY;
Get all remaining events...
SELECT * FROM data WHERE end >= NOW() + INTERVAL 14 DAY;
Basically, is it possible to join these into one query?
SELECT * FROM data
ORDER BY (logic 1), (logic 2), (logic 3);
Alternatively, I did get it working with running 3 separate queries and building up the result array on the server-side, but would like to simplify my code if possible.
Hoping that an end result will always show a list of events that will be expiring within 7 days first, then events that are happening between 7 - 14 days (could be starting or ongoing), then events that are still ongoing or starting after 14 days from today.

Answer 1

Depending on your SQL database, you can do something like this:
SELECT * FROM data
WHERE (end < NOW() + INTERVAL 7 DAY) -- logic 1
or (NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY) -- logic 2
or (NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY) -- logic 3
order by
case
when (end < NOW() + INTERVAL 7 DAY) then 1
when (NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY) then 2
when (NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY) then 3
else 4
end asc
;
You may also use union all:
SELECT 1 as sort_order, * FROM data
WHERE (end < NOW() + INTERVAL 7 DAY)
union all
SELECT 2 as sort_order, * FROM data
WHERE (NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY)
union all
SELECT 3 as sort_order, * FROM data
where NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY
The sort_order is probably not needed, but if you get your result not in the order of select, you may then use a subquery; also your database might forbids you from using order by in an union all.
select *
from (
SELECT 1 as sort_order, * FROM data
WHERE (end < NOW() + INTERVAL 7 DAY)
union all
SELECT 2 as sort_order, * FROM data
WHERE (NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY)
union all
SELECT 3 as sort_order, * FROM data
where NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY
) order by sort_order asc -- and any other key
I would personally go for the union all if possible (it is more readable).

Answer 2

You could try using a UNION where you select the data set and have a column that has the order you want. e.g.
SELECT 1 as orderby,* FROM data WHERE end < NOW() + INTERVAL 7 DAY;
UNION ALL
SELECT 2, * FROM data WHERE NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY
UNION ALL
SELECT 3, * FROM data WHERE end >= NOW() + INTERVAL 14 DAY
ORDER BY orderby, end
P.S. I would suggest you don't use SQL Keywords such as end for column names in your database, that can sometimes cause issues, enddate would be a better column name.
P.P.S. Avoid doing SELECT *, it is better to explicitly list the columns that you want.

Answer 3

I assume you are using MySQL.
use the case when .. then .. end in the select clause, then order by this column.
select *, case
when end < NOW() + INTERVAL 7 DAY then 1
when NOW() + INTERVAL 7 DAY >= start AND end < NOW() + INTERVAL 14 DAY then 2
else 3 as priority
from data
order by priority
Also, you can use the case in the order by clause.
Note: I didn't take care of your business logic, so test it well, just giving you how you can achieve it, hope it helps.