跟一个朋友，不错公司的主管交流时，对于mysql中条件查询和排序时 与索引的关系

mysql> explain select * from article where title=‘希望光伏企业挺过2个月‘ o

rder by id desc\\\\\\\\G

*************************** 1. row ***************************

           id: 1

  select_type: SIMPLE

        table: article

         type: index

possible_keys: NULL

          key: PRIMARY

      key_len: 4

          ref: NULL

         rows: 567

        Extra: Using where

1 row in set (0.00 sec)

mysql> select * from article where title=‘希望光伏企业挺过2个月‘;

+----+-------------+---------+--------+-----------------------------+----------+

-----------+-------+-------------+---------+---------+--------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------+--------+--

---------+--------+------------+------------+

| id | category_id | user_id | app_id | title                       | subtitle |

 professor | money | cooperation | project | address | discription

                                                                    | source | r

ecommend | status | ctime      | mtime      |

+----+-------------+---------+--------+-----------------------------+----------+

-----------+-------+-------------+---------+---------+--------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------+--------+--

---------+--------+------------+------------+

| 10 |           2 |       4 |      0 | 希望光伏企业挺过2个月 |          |

           |     0 |             |         |         | 希望企业挺过两个月。 |        |

        1 |      0 | 1371524848 | 1371525226 |

+----+-------------+---------+--------+-----------------------------+----------+

-----------+-------+-------------+---------+---------+--------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------+--------+--

---------+--------+------------+------------+

1 row in set (0.00 sec)

mysql> explain select * from article where title=‘希望光伏企业挺过2个月‘;

+----+-------------+---------+------+---------------+------+---------+------+---

---+-------------+

| id | select_type | table   | type | possible_keys | key  | key_len | ref  | ro

ws | Extra       |

+----+-------------+---------+------+---------------+------+---------+------+---

---+-------------+

|  1 | SIMPLE      | article | ALL  | NULL          | NULL | NULL    | NULL |  5

67 | Using where |

+----+-------------+---------+------+---------------+------+---------+------+---

---+-------------+

1 row in set (0.00 sec)

大部门的开发人员会认为第一种查询时，不会用到索引

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mysql中条件查询加排序和索引的关系