哪个mysql构造更快？

Question

SELECT ... WHERE COL IN(A,B) 

or 

SELECT ... WHERE (COL = A or COL = B)

我试图找出这两种结构之间的区别是什么？
如果用于接近100万大关的结果集,是否会有显着的性能提升？

Answer 1

mysql> describe select * from users where id = 1 or id = 2;
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
| id | select_type | table | type  | possible_keys | key     | key_len | ref  | rows | Extra       |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
|  1 | SIMPLE      | users | range | PRIMARY       | PRIMARY | 4       | NULL |    2 | Using where |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
1 row in set (0.01 sec)

mysql> describe select * from users where id in (1,2);
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
| id | select_type | table | type  | possible_keys | key     | key_len | ref  | rows | Extra       |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
|  1 | SIMPLE      | users | range | PRIMARY       | PRIMARY | 4       | NULL |    2 | Using where |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
1 row in set (0.00 sec)

从DESCRIBE陈述的输出来看- 它们是相同的.