mysql – 我可以使用外键索引作为获取INNODB表中行数的快捷方式吗?
我有一个包含大量行的表.
默认情况下,主键(自动递增整数)已编制索引.
在等待返回行计数时,我在另一个窗口中执行了EXPLAIN,结果如下:
mysql> SELECT COUNT(1) FROM `gauge_data`;
+----------+
| COUNT(1) |
+----------+
| 25453476 |
+----------+
1 row in set (2 min 36.20 sec)
mysql> EXPLAIN SELECT COUNT(1) FROM `gauge_data`;
+----+-------------+------------+-------+---------------+-----------------+---------+------+----------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------+-------+---------------+-----------------+---------+------+----------+-------------+
| 1 | SIMPLE | gauge_data | index | NULL | gauge_data_FI_1 | 5 | NULL | 24596487 | Using index |
+----+-------------+------------+-------+---------------+-----------------+---------+------+----------+-------------+
1 row in set (0.13 sec)
由于主键保证是唯一的,我可以从EXPLAIN中获取行数并将其用作表的行数吗?
顺便说一句,我认为数字的差异是由于更多数据不断被添加到该表中.