Направете своя thread_title
е
varchar(255) and Default value is NULL
и използвайте вашата заявка
CREATE TABLE IF NOT EXISTS `forumposts` (
`thread_title` varchar(255) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
INSERT INTO `forumposts` (`thread_title`) VALUES
('foo'),
('bar'),
(NULL);
SELECT thread_title FROM forumposts WHERE thread_title IS NOT NULL
ИЗХОД
THREAD_TITLE
foo
bar