Returning query results in predefined order

问题

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 nothing more than the ID field?

Statements SELECT id FROM table WHERE id in (7,2,5,9,8); and SELECT id FROM table WHERE id in (8,2,5,9,7); both return them in the same order.

回答1:

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.

回答2:

ORDER BY FIELD(ID,7,2,4,5,8) is your best bet, but it's still ugly.

回答3:

Could you include a case expression that maps your IDs 7,2,5,... to the ordinals 1,2,3,... and then order by that expression?

回答4:

All ordering is done by the ORDER BY keywords, you can only however sort ascending and descending. If you are using a language such as PHP you can then sort them accordingly using some code but I do not believe it is possible with MySQL alone.

回答5:

This works in Oracle. Can you do something similar in MySql?

SELECT ID_FIELD
FROM SOME_TABLE
WHERE ID_FIELD IN(11,10,14,12,13)
ORDER BY
  CASE WHEN ID_FIELD = 11 THEN 0
       WHEN ID_FIELD = 10 THEN 1
       WHEN ID_FIELD = 14 THEN 2
       WHEN ID_FIELD = 12 THEN 3
       WHEN ID_FIELD = 13 THEN 4
  END

回答6:

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.

回答7:

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.

回答8:

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.

回答9:

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.

回答10:

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.

回答11:

Best I can think of is adding a second Column orderColumn:

And then just do a ORDER BY orderColumn

来源：https://stackoverflow.com/questions/134379/returning-query-results-in-predefined-order

标签

mysql

sql-order-by