Complex order by mysql - mysql

Question

if I have a table like this
+----+----------------+
| id | id_alternativo |
+----+----------------+
| 15 | 18 |
+----+----------------+
| 16 | 0 |
+----+----------------+
| 17 | 0 |
+----+----------------+
| 18 | 0 |
+----+----------------+
How can I order records to show id 18 after id 15?

Answer 1

Looking at the MySQL documentation you can use multiple columns in your sort and use DESC/ASC per column.
http://dev.mysql.com/doc/refman/5.7/en/order-by-optimization.html
If I understand correctly what you mean your query will look as followed:
SELECT id, id_alternativo FROM table ORDER BY id_alternativo DESC, id DESC;
+------+----------------+
| id | id_alternativo |
+------+----------------+
| 15 | 18 |
| 18 | 0 |
| 17 | 0 |
| 16 | 0 |
+------+----------------+

Answer 2

One solution is to use a self join like this:
select t.*
from
yourtable t left join yourtable o
on t.id = o.id_alternativo
order by
coalesce(o.id, t.id), t.id
this will put all alternative ids after the main id (in this case 18 will follow 15).
Please see a fiddle here. Please note that this will work unless an alternative id has another alternative id (e.g. if 18 itself has another alternative id) but this cannot be solved purely with MySQL as it does not support recursive queries yet.

Answer 3

from what I understand just use order by id (18, 15) and any other id you need.

Answer 4

select id,id_alternativo
from table_name
order by case id when 15 Then 1
when 18 Then 2
when 16 Then 3
when 17 Then 4
else 5
end;

Answer 5

you can use order like this:
SELECT id
FROM mytab
ORDER BY IF(id=18,155,id*10);
sample
MariaDB []> select id from mytab;
+----+
| id |
+----+
| 1 |
| 2 |
| 3 |
| 4 |
| 9 |
| 10 |
| 11 |
| 12 |
| 13 |
| 14 |
| 15 |
| 16 |
| 17 |
| 18 |
| 19 |
+----+
15 rows in set (0.00 sec)
MariaDB []> SELECT id
-> FROM mytab
-> ORDER BY IF(id=18,155,id*10);
+----+
| id |
+----+
| 1 |
| 2 |
| 3 |
| 4 |
| 9 |
| 10 |
| 11 |
| 12 |
| 13 |
| 14 |
| 15 |
| 18 |
| 16 |
| 17 |
| 19 |
+----+
15 rows in set (0.00 sec)
MariaDB []>

Answer 6

Sorry, I used a simple example but my table is more complex. The id_alternativo can be recursive (id 18 could have an id_alternativo = 19) and so on and id_alternativo could not be the most high id on table so ORDER BY id_alternativo DESC, id DESC doesn't work. Here's a query from my table:
SELECT
a.id, a.compatibile, a.id_alternativo
FROM
ordini_righe AS a
WHERE
intestazione IN (398010) AND a.canc = 0
AND a.stato_ordine = 0
Here's the result
+-------+-------------+----------------+
| id | compatibile | id_alternativo |
+-------+-------------+----------------+
|828924 | 0 | 828931 |
+-------+-------------+----------------+
|828925 | 828932 | 0 |
+-------+-------------+----------------+
|828926 | 0 | 0 |
+-------+-------------+----------------+
|828927 | 0 | 0 |
+-------+-------------+----------------+
|828931 | 0 | 828933 |
+-------+-------------+----------------+
|828932 | 828932 | 0 |
+-------+-------------+----------------+
|828933 | 0 | 0 |
+-------+-------------+----------------+
I had to order compatibile desc and then order the other records by the relation beetween id_alternativo and id. So i solved using a new column like this
SELECT
a.id, a.compatibile, a.id_alternativo, IF(id_alternativo = 0, a.id, id_alternativo) ordine
FROM
ordini_righe AS a
JOIN
locazioni AS b ON a.locazione = b.id
JOIN
stati_righe AS c ON a.stato_ordine = c.id
WHERE
intestazione IN (398010) AND a.canc = 0
AND a.stato_ordine = 0
ORDER BY compatibile DESC, ordine, a.id ASC
And I got the desired result
+-------+-------------+----------------+--------+
| id | compatibile | id_alternativo | ordine |
+-------+-------------+----------------+--------+
|828925 | 828932 | 828931 | 828925 |
+-------+-------------+----------------+--------+
|828932 | 828932 | 0 | 828932 |
+-------+-------------+----------------+--------+
|828926 | 0 | 0 | 828926 |
+-------+-------------+----------------+--------+
|828927 | 0 | 0 | 828927 |
+-------+-------------+----------------+--------+
|828924 | 0 | 828931 | 828931 |
+-------+-------------+----------------+--------+
|828931 | 0 | 828933 | 828933 |
+-------+-------------+----------------+--------+
|828933 | 0 | 0 | 828933 |
+-------+-------------+----------------+--------+