一、检索单列
>SELECT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;
DISTINCT: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(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MariaDB|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
