2019独角兽企业重金招聘Python工程师标准>>> 
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 <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 | |
