I'm still trying to decript the EXPLAIN result, and there is something I really don't understand:
mysql> EXPLAIN SELECT STRAIGHT_JOIN media.* FROM country,content,media WHERE country.id='Germany' AND country.detail_tid=content.tid AND content.id=media.content_id; On the FAST server: +--+-------+-----+----------+----------+----+----------+----+ |id|table |type |possible_k|key |k_le|ref |rows| +--+-------+-----+----------+----------+----+----------+----+ |1 |country|const|PRIMARY |PRIMARY |383 |const | 1| |1 |content|ALL |PRIMARY |NULL |NULL|NULL | 137| |1 |media |ref |media_FI_2|media_FI_2|5 |content.id| 248| +--+-------+-----+----------+----------+----+----------+----+ On the SLOW server: +--+-------+-----+----------+----------+----+----------+------+ |id|table |type |possible_k|key |k_le|ref | rows | +--+-------+-----+----------+----------+----+----------+------+ |1 |country|ref |PRIMARY |PRIMARY |383 |const | 1| |1 |content|ALL |PRIMARY |NULL |NULL|NULL | 137| |1 |media |ALL |media_FI_2|NULL |NULL|NULL |125649| +--+-------+-----+----------+----------+----+----------+------+ On the 3rd row, on the fast server, type=ref, and ref points toward the content.id column. And on the slow server, type=ALL, and ref points to NULL. Since my MySql schema defines explicitly the foreign key, should'n I have 'content.id' instead of 'NULL' ? What is the difference between 'possible_key' and 'key' columns ? why key=NULL on my slow server ? Tristan -- Tristan Marly http://www.linkedin.com/in/tristanmarly -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
