一、检索单列

>  列名 FROMM 表名;

二、 检索多列

> SELECT 列名1, 列名2, 列名3...

    FROM 表名;

三、 检索所有的列

> SELECT * FROM 表名;

四、 去除重复列

> SELECT DISTINCT 列名 FROM 表名;

: 去除重复行

五、 限制检索数

> SELECT 列名 FROM 表 LIMIT 4;

刷选所用数据中的前4行;

六、 基本排序

升序: 默认 <ASC>(ascending order);

降序:**DESC**(descending order);

    > SELECT * FROM books ORDER BY book_id;

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

| book_id | book_name        | book_author_name | publication_date | description | classify | c    |

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

|       1 | 跟我学    | NULL             | 2016-12-03       | NULL        | 18       | NULL |

|       2 | NodeJS           | NULL             | 2016-12-02       | NULL        | 18       | NULL |

|       3 | HTTP权威指南     | NULL             | 2002-01-01       | NULL        | 18       | NULL |

> SELECT * FROM books ORDER BY book_id DESC;

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

| book_id | book_name        | book_author_name | publication_date | description | classify | c    |

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

|      22 | 巨人的陨落       | NULL             | 2016-05-01       | NULL        | 11       | NULL |

|      21 | 史记             | NULL             | 1982-11-01       | NULL        | 11       | NULL |

|      20 | 国史大纲         | NULL             | 2013-08-01       | NULL        | 11       | NULL |

|      19 | 人类简史         | NULL             | 2014-11-01       | NULL        | 11       | NULL |

七、 按列的位置排序

SELECT book_id, book_name, description FROM books ORDER BY 2, 3; 表示先按book_n