php - 我的 sql 查询有改进吗？

Question

是否有任何方法可以用其他东西删除 MAX，也许是 ASC LIMIT 1 以减少数据库限制？我的查询获取最大 ID 并将其加 1。

这是我的查询:

$query = 'SELECT MAX(ID) +1 as maxidpost  
          FROM wp_posts';
$result = mysql_query($query) or die(mysql_error());
while($row = mysql_fetch_array($result)) {
  echo 'p='. $row['maxidpost'];
}
mysql_close();

Answer 1

关于您的查询，数据库告诉您什么？如果 id 被索引，那么

mysql> explain select max(id) + 1 from times;
+----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra                        |
+----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
|  1 | SIMPLE      | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL | Select tables optimized away |
+----+-------------+-------+------+---------------+------+---------+------+------+------------------------------+
1 row in set (0.18 sec)

mysql> explain select id from times order by id ASC limit 1;
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
| id | select_type | table | type  | possible_keys | key     | key_len | ref  | rows | Extra       |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
|  1 | SIMPLE      | times | index | NULL          | PRIMARY | 4       | NULL |    1 | Using index |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
1 row in set (0.00 sec)