Preserve order of SQL WHERE IN() clause with nested SELECT

Question

I need a list of item names ordered by count of items. Item names and corresponing id's are stored in tabletwo while tableone refers to items by id's:

      tableone              tabletwo
+--------+-----------+    +----+------+
| itemid | condition |    | id | name |
+--------+-----------+    +----+------+
| 2      | satisfied |    | 1  | foo  |
+--------+-----------+    +----+------+
| 1      | satisfied |    | 2  | bar  |
+--------+-----------+    +----+------+
| 3      | satisfied |    | 3  | hurr |
+--------+-----------+    +----+------+
| 3      | satisfied |    | 4  | durr |
+--------+-----------+    +----+------+
| 3      | satisfied |
+--------+-----------+
| 4      | satisfied |
+--------+-----------+
| 4      | satisfied |
+--------+-----------+
| 3      | nope      |
+--------+-----------+
| 1      | satisfied |
+--------+-----------+

SQL code:

SELECT `itemname` FROM `tabletwo` WHERE `id` IN (
    SELECT `itemid` FROM (
        SELECT count(`itemid`), `itemid`
        FROM `tableone`
        WHERE `some_codition`="satisfied"
        GROUP BY `itemid`
        ORDER BY count(`itemid`) DESC
    ) alias
)

The nested SELECT returns a list of item id's in descendant order: 3, 4, 1, 2 . This list is then used as an argument of an IN() clause. The expected result of the whole query is: hurr, durr, foo, bar (in this exact order). But the order is not preserved. I know it can be done like this: ORDER BY FIELD(id, 3, 4, 1, 2) but I don't know how to do this trick when the ordered list is fetched dynamically like in my case. Do I need to SELECT it again? Or temporary table maybe? Or is it better to build another query outside SQL?

Answer 1

Use JOIN instead of IN :

SELECT
    t2.name
FROM tabletwo t2
LEFT JOIN tableone t1
    ON t1.itemid = t2.id
    AND t1.`condition` = 'satisfied'
GROUP BY
    t2.id, t2.name
ORDER BY COUNT(*) DESC

If you want to exclude rows from tabletwo that do not have a match on tableone , use INNER JOIN instead of LEFT JOIN .

ONLINE DEMO

Answer 2

Try using JOIN instead:

SELECT t2.`itemname` 
FROM `tabletwo` AS t2
JOIN (    
   SELECT count(`itemid`) AS cnt, `itemid`
   FROM `tableone`
   WHERE `some_codition`="satisfied"
   GROUP BY `itemid`
) AS t1 ON t1.`itemid` = t2.`id`
ORDER BY t1.cnt DESC

You can create a derived table using the subquery of the IN operator and perform a JOIN to this table, so that you are able to use the COUNT in the ORDER BY clause of the main query.