27Sep/060
Empty Set Equality
SELECT 1 LIMIT 0; Empty set (0.00 sec) SELECT 2 LIMIT 0; Empty set (0.00 sec) SELECT NULL LIMIT 0; Empty set (0.00 sec)
Exactly what I'd expect. So here's the question:
SELECT '1 = 1' AS equality, (SELECT 1 LIMIT 0) = (SELECT 1 LIMIT 0) AS result UNION SELECT '1 = 2', (SELECT 1 LIMIT 0) = (SELECT 2 LIMIT 0) UNION SELECT '1 = NULL', (SELECT 1 LIMIT 0) = (SELECT NULL LIMIT 0);
What do you think? Are all empty sets created identical?
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12Sep/0610
Single-query UNION with LIMIT and ORDER
I have a query that behaves differently in every version of MySQL I've tried. Could you do me a favor? Run the following four lines and post a comment with your results. And if you know of a particular bug fix that addresses this issue, let me know about that too.
CREATE TABLE `test` (`id` tinyint); INSERT INTO test VALUES (1), (2), (3), (4), (5); SHOW VARIABLES LIKE 'version%'; (SELECT * from test ORDER BY id DESC LIMIT 3) ORDER BY id ASC;