Question

I’d like to select all the rows from a temporary table that have a value equal to the maximum value.

TEMPORARY TABLE test

id | value
1  | 7
2  | 6
3  | 7

Expected result:

id | value
1  | 7
3  | 7

I’ve already tried several things but all attempts (except creating another temporary table with the same content) failed so far because of “You cannot refer to a TEMPORARY table more than once in the same query.” (Source: http://dev.mysql.com/doc/refman/5.0/en/temporary-table-problems.html).
Is there a possibility to do this in a more “elegant” way than copying the table and its contents?

What I’ve tested so far:

SELECT table1.* FROM test table1 LEFT JOIN test table2 ON table1.value < table2.value     
WHERE table2.value IS NULL;
SELECT * FROM test WHERE value = (SELECT MAX(value) FROM test);

And this is my current solution:

CREATE TEMPORARY TABLE test2 (...);
INSERT INTO test2 SELECT * FROM test;
SELECT * FROM test WHERE value = (SELECT MAX(value) FROM test2);

Answer 1

You could try using variables. The following will scan the test table only once (not-tested):

SELECT   test.*, 
         @curMax := IF(@curMax = -1, value, @curMax)
FROM     test,
         (SELECT @curMax := -1) r
HAVING   @curMax = value OR @curMax = -1
ORDER BY value DESC;