Mysql 数据库查询执行时间

当我使用以下方法计算行数时，总共需要4分钟51.62秒

mysql> select count(*) from result where id < 1000000;
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (4 min 51.62 sec)

mysql> select count(*) from result where id < 500000;
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (0.14 sec)

mysql> select count(*) from result where id < 600000;
1 row in set (0.21 sec)

mysql> select count(*) from result where id < 700000;
1 row in set (0.28 sec)

mysql> select count(*) from result where id < 800000;
1 row in set (0.23 sec)

mysql> select count(*) from result where id < 900000;
1 row in set (0.26 sec)

mysql> select count(*) from result where id < 950000;
1 row in set (0.27 sec)

mysql> select count(*) from result where id < 1000000;
1 row in set (39.66 sec)

但是,

当我使用以下方法将行数计算为增加id时，总共需要41.05秒

mysql> select count(*) from result where id < 1000000;
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (4 min 51.62 sec)

mysql> select count(*) from result where id < 500000;
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (0.14 sec)

mysql> select count(*) from result where id < 600000;
1 row in set (0.21 sec)

mysql> select count(*) from result where id < 700000;
1 row in set (0.28 sec)

mysql> select count(*) from result where id < 800000;
1 row in set (0.23 sec)

mysql> select count(*) from result where id < 900000;
1 row in set (0.26 sec)

mysql> select count(*) from result where id < 950000;
1 row in set (0.27 sec)

mysql> select count(*) from result where id < 1000000;
1 row in set (39.66 sec)

---

谁能给我解释一下，为什么会这样，它就像批处理或缓存一样。我不知道为什么会这样？提前感谢。

id 950000到1000000插入多行错误

可能正在兑现，但请查看每个行的执行计划，看看是否可以找到任何有趣的内容重置查询缓存；并从id<600000的结果运行select count*；再一次这应该可以解释为什么它跑得更快