mysql order by with union doesn't seem to work

问题

Here is my query

(SELECT * FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%only three doors%" OR `joke` LIKE "%only three doors%") ORDER BY `ups` DESC,`downs` ASC)
UNION
(SELECT * FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%only%" OR `joke` LIKE "%only%") ORDER BY `ups` DESC,`downs` ASC)
UNION
(SELECT * FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%three%" OR `joke` LIKE "%three%") ORDER BY `ups` DESC,`downs` ASC)
UNION
(SELECT * FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%doors%" OR `joke` LIKE "%doors%") ORDER BY `ups` DESC,`downs` ASC)
 LIMIT 0, 30

For some reason it doesn't seem to order by ups or downs...it just tosses me back the results in the order they are naturally in the database.

When I cut it down to only one query, it works fine, but other than that, it seems to ignore it.

I also don't want to order by the entire results, or I would have put LIMIT 0,30 Order By blah

回答1:

From MySQL documentation:

... use of ORDER BY for individual SELECT statements implies nothing about the order in which the rows appear in the final result because UNION by default produces an unordered set of rows.

Basically the only time an ORDER in a union will be useful is if you are using LIMIT as well.

So if you query was like this:

(SELECT * FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%only three doors%" OR `joke` LIKE "%only three doors%") ORDER BY `ups` DESC,`downs` ASC LIMIT 10)
UNION ...

Then you would see the first ten records that would be returned based on that order, but they wouldn't necessarily be displayed in order.

UPDATE:

Try this -

(SELECT *, 1 as ob FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%only three doors%" OR `joke` LIKE "%only three doors%") )
UNION
(SELECT *, 2 as ob FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%only%" OR `joke` LIKE "%only%") )
UNION
(SELECT *, 3 as ob FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%three%" OR `joke` LIKE "%three%") )
UNION
(SELECT *, 4 as ob FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%doors%" OR `joke` LIKE "%doors%"))
 ORDER BY `ob`, `ups` DESC,`downs` ASC LIMIT 0, 30

回答2:

I got solution for this:

SELECT *
FROM (
    (SELECT 1 as SortRank, uid, title, state, zip, region,cantone FROM company WHERE city=".$city." AND region=".$region." AND cantone=".$cantone.")
     UNION
    (SELECT 2 as SortRank, uid, title, state, zip, region,cantone FROM company WHERE region=".$region." AND cantone=".$cantone.")
    union all
    (SELECT 3 as SortRank, uid, title, state, zip, region,cantone FROM company WHERE cantone=".$cantone.")
) As u
GROUP BY uid 
ORDER BY SortRank,state=2, title ASC
LIMIT 0,10

In above query i want result eg. first show all records with city, region and cantone then if city not available then show all records with region and cantone and then all records with cantone of city. So, removing repeating records i used GROUP BY clause, it will sort all records based on query group then all records with state=2.

回答3:

What the query does, is to order each sub-query separately and unifying all of them. There is no guarantee the result would be ordered.

what you need to do is to order the unified query as such:

Select * from (
  (SELECT *, 1 as `p` FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%only three doors%" OR `joke` LIKE "%only three doors%"))
  UNION
  (SELECT *, 2 as `p` FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%only%" OR `joke` LIKE "%only%"))
  UNION
   (SELECT *, 3 as `p` FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%three%" OR `joke` LIKE  "%three%"))
  UNION
  (SELECT *, 4 as `p` FROM `jokes` WHERE `flags` < 5 AND (`title` LIKE "%doors%" OR `joke` LIKE "%doors%"))
    ) ORDER BY `p` ASC, `ups` DESC,`downs` ASC

回答4:

You should be able to use UNION ALL to remove duplicate removal (and also complete result set sorting). Using that the result set should be in the order of the select statements in the query.

来源：https://stackoverflow.com/questions/8685168/mysql-order-by-with-union-doesnt-seem-to-work