Returning query results in predefined order

Question

Is it possible to do a SELECT statement with a predetermined order, ie. selecting IDs 7,2,5,9 and 8 and returning them in that order, based on

Answer 1

It's hacky (and probably slow), but you can get the effect with UNION ALL:

SELECT id FROM table WHERE id = 7
UNION ALL SELECT id FROM table WHERE id = 2
UNION ALL SELECT id FROM table WHERE id = 5
UNION ALL SELECT id FROM table WHERE id = 9
UNION ALL SELECT id FROM table WHERE id = 8;

Edit: Other people mentioned the find_in_set function which is documented here.

Answer 2

You may need to create a temp table with an autonumber field and insert into it in the desired order. Then sort on the new autonumber field.

Answer 3

Erm, not really. Closest you can get is probably:

SELECT * FROM table WHERE id IN (3, 2, 1, 4) ORDER BY id=4, id=1, id=2, id=3

But you probably don't want that :)

It's hard to give you any more specific advice without more information about what's in the tables.

Answer 4

I didn't think this was possible, but found a blog entry here that seems to do the type of thing you're after:

SELECT id FROM table WHERE id in (7,2,5,9,8) 
ORDER BY FIND_IN_SET(id,"7,2,5,9,8");

will give different results to

SELECT id FROM table WHERE id in (7,2,5,9,8) 
ORDER BY FIND_IN_SET(id,"8,2,5,9,7");

FIND_IN_SET returns the position of id in the second argument given to it, so for the first case above, id of 7 is at position 1 in the set, 2 at 2 and so on - mysql internally works out something like

id | FIND_IN_SET
---|-----------
7  | 1
2  | 2
5  | 3

then orders by the results of FIND_IN_SET.

Answer 5

You get answers fast around here, don't you…

The reason I'm asking this is that it's the only way I can think of to avoid sorting a complex multidimensional array. I'm not saying it would be difficult to sort, but if there were a simpler way to do it with straight sql, then why not.

Answer 6

One Oracle solution is:

SELECT id FROM table WHERE id in (7,2,5,9,8)
ORDER BY DECODE(id,7,1,2,2,5,3,9,4,8,5,6);

This assigns an order number to each ID. Works OK for a small set of values.