Put a specific row first and then order by a column - mysql

Question

EDIT: The goal is to order the output so that the first result is the row with store_id = 5 and the maximum rank of all items with store_id = 5. Then the rest of the deals are ranked according to their rank in descending order, regardless of their store_id. For the actual query, a union would be too expensive.
An example of data would be:
+----+----------+------+
| id | store_id | rank |
+----+----------+------+
| 1 | 1 | 10 |
+----+----------+------+
| 2 | 5 | 9 |
+----+----------+------+
| 3 | 4 | 8 |
+----+----------+------+
| 4 | 3 | 7 |
+----+----------+------+
| 5 | 3 | 6 |
+----+----------+------+
| 6 | 1 | 5 |
+----+----------+------+
The final query being run would be:
SELECT id,store_ID,IF(#id=id,rank=rank*9999999,rank) AS rank
FROM (
SELECT * FROM (
SELECT id,rank,store_id
FROM items
) b
JOIN (#id:=(SELECT id FROM b WHERE store_id = 5 ORDER BY rank DESC LIMIT 1)) AS s
)
ORDER BY rank DESC
And the desired outcome would be:
+----+----------+------+
| id | store_id | rank |
+----+----------+------+
| 2 | 5 | 9 |
+----+----------+------+
| 1 | 1 | 10 |
+----+----------+------+
| 3 | 4 | 8 |
+----+----------+------+
| 4 | 3 | 7 |
+----+----------+------+
| 5 | 3 | 6 |
+----+----------+------+
| 6 | 1 | 5 |
+----+----------+------+
Here (#id:=(SELECT id FROM b WHERE store_id = 5 ORDER BY rank DESC LIMIT 1)) is being used to select the top scoring item with store_id = 5. This item is meant to appear first in the list, hence why it is reranked by multiplying it by a very large number. All other ranks remain untouched and are ranked according to their score in descending order.
The problem is that the select statement in the join is trying to join a selection from a subquery called b. However, table b does not actually exist in the database, so MySQL is saying that table b does not exist. How can I reference the subquery? The actual subquery is incredibly complex, so I haven't included it here, but if interested you can see a version of it here: MySQL - How To Optimize thie Query. The query in this question is just to keep the problem simple.

Answer 1

You can adjust your order by clause to put a specific row first. Let's say you wanted store_id 5 to be first, you can do this:
ORDER BY store_id = 5 DESC, rank DESC;
Which will put the row with store_id 5 on top. In this example, you want the row that has the highest rank for store_id 5, so I wrote the following subquery:
SELECT id
FROM myTable
WHERE store_id = 5
ORDER BY rank DESC
LIMIT 1;
And I put that in the ORDER BY clause:
SELECT *
FROM myTable
ORDER BY id =
(SELECT id FROM myTable WHERE store_id = 5 ORDER BY rank DESC LIMIT 1) DESC,
rank DESC;
Here is an SQL Fiddle.
EDIT
If you put a subquery in your FROM clause, you won't be able to reference its alias in the subquery of the ORDER BY clause. However, in a very unreadable fashion, you can put the same subquery there to accomplish it, like this:
SELECT *
FROM (SELECT * FROM myTable) b
ORDER BY id =
(SELECT id FROM (SELECT * FROM myTable) b WHERE store_id = 5 ORDER BY rank DESC LIMIT 1) DESC,
rank DESC;
Another Fiddle.