第一部分基本SELECT
1.1 检索单列
> SELECT 列名 FROMM 表名;
1.2 检索多列
> SELECT 列名1, 列名2, 列名3...
FROM 表名;
1.3 检索所有的列
> SELECT * FROM 表名;
1.4 去除重复列DISTINCT: 去除重复行
> SELECT DISTINCT 列名 FROM 表名;
1.5 限制检索数
> SELECT 列名 FROM 表 LIMIT 4;
1.6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 |
