两条SQL语句比较，哪个好点

Question

explain 出来的结果。。+----+-------------+-------+--------+---------------+------------+---------+--------------------------------------+------+--------------------------+
| id | select_type | table | type   | possible_keys | key        | key_len | ref                                  | rows | Extra                    |
+----+-------------+-------+--------+---------------+------------+---------+--------------------------------------+------+--------------------------+
|  1 | SIMPLE      | pd    | range  | PRIMARY       | PRIMARY    | 8       | NULL                                 |  168 | Using where; Using index |
|  1 | SIMPLE      | p     | eq_ref | PRIMARY       | PRIMARY    | 4       | kleehaus_wedding.pd.product_id       |    1 | Using where              |
|  1 | SIMPLE      | p2s   | eq_ref | PRIMARY       | PRIMARY    | 8       | kleehaus_wedding.pd.product_id,const |    1 | Using where; Using index |
|  1 | SIMPLE      | ps    | ref    | product_id    | product_id | 4       | kleehaus_wedding.p.product_id        |    1 | Using index              |
+----+-------------+-------+--------+---------------+------------+---------+--------------------------------------+------+--------------------------++----+-------------+-------+--------+---------------------+-------------+---------+---------------------------------------+------+--------------------------+
| id | select_type | table | type   | possible_keys       | key         | key_len | ref                                   | rows | Extra                    |
+----+-------------+-------+--------+---------------------+-------------+---------+---------------------------------------+------+--------------------------+
|  1 | SIMPLE      | p2c   | ref    | PRIMARY,category_id | category_id | 4       | const                                 |  436 | Using where              |
|  1 | SIMPLE      | pd    | eq_ref | PRIMARY             | PRIMARY     | 8       | kleehaus_wedding.p2c.product_id,const |    1 | Using where; Using index |
|  1 | SIMPLE      | p     | eq_ref | PRIMARY             | PRIMARY     | 4       | kleehaus_wedding.p2c.product_id       |    1 | Using where              |
|  1 | SIMPLE      | ps    | ref    | product_id          | product_id  | 4       | kleehaus_wedding.p.product_id         |    1 | Using index              |
|  1 | SIMPLE      | p2s   | eq_ref | PRIMARY             | PRIMARY     | 8       | kleehaus_wedding.pd.product_id,const  |    1 | Using where; Using index |
+----+-------------+-------+--------+---------------------+-------------+---------+---------------------------------------+------+--------------------------+
第一个SQL，TYPE为range,扫描的行数只有168,运行的速度为:0.02sec
第二个SQL, TYPE为ref,扫描的行数为436,运行的速度为:0.02sec - 0.03sec从上面EXPLAIN出来的数据，哪个SQL会更好些。。

Answer 1

没有版表结构、SQL语句，只从扫描的行数来看，似乎第1个要好些

Answer 2

看explain的效果应该是第一个好点

Answer 3

但我有个疑问，为什么show processlist的时候，第一个SQL经常都会出现的？？？但执行的效率并不低。

Answer 4

似乎你应该先把SQL贴出来，并把表关系和索引关系贴出来，这样给你的建议才会更全面一点