# MySql 数据库
# 一、数据分析
# 1、文本传值
<a href="/details.php?title=URL跳转">URL跳转</a>
# 2、文章表：主键
RDBMS术语：主键是唯一的，一个数据表中只能包含一个主键，你可以使用主键来查询数据。
ALTER TABLE `article`
ADD COLUMN `id` int(10) UNSIGNED NOT NULL AUTO_INCREMENT COMMENT '文章主键' FIRST ,
ADD PRIMARY KEY (`id`);
# 3、主键传值
<a href="/details.php?id=1">URL跳转</a>
# 4、分类表：主键
ALTER TABLE `class`
ADD COLUMN `id` int(10) UNSIGNED NOT NULL AUTO_INCREMENT COMMENT '主键' FIRST ,
ADD PRIMARY KEY (`id`);
# 5、分类表：排序字段
ALTER TABLE `class`
ADD COLUMN `sort` int(10) UNSIGNED NULL DEFAULT 0 COMMENT '排序' AFTER `name`;
# 6、文章表：分类主键
ALTER TABLE `article`
ADD COLUMN `class` int(10) UNSIGNED NULL DEFAULT 0 COMMENT '分类ID' AFTER `date`;
# 二、比较运算符
| 符号 | 描述 |
|---|
= | 等号 |
<> | 不等于 |
> | 大于 |
< | 小于 |
>= | 大于等于 |
<= | 小于等于 |
SELECT * FROM `article` WHERE `id` = 6;
SELECT * FROM `article` WHERE `id` <> 6;
SELECT * FROM `article` WHERE `id` > 6;
SELECT * FROM `article` WHERE `id` < 6;
SELECT * FROM `article` WHERE `id` >= 6;
SELECT * FROM `article` WHERE `id` <= 6;
# 三、逻辑运算符
| 符号 | 描述 |
|---|
NOT | 逻辑非，取反 |
AND | 逻辑与 |
OR | 逻辑或 |
XOR | 逻辑异或 |
SELECT * FROM `article` WHERE NOT(`id` = 1);
SELECT * FROM `article` WHERE `class` = 2 AND `date` = '2021-02-01';
SELECT * FROM `article` WHERE `class` = 2 OR `date` = '2021-02-01';
SELECT * FROM `article` WHERE `id` = 1 XOR `id` = 2;
SELECT * FROM `article` WHERE `id` = 1 XOR `id` = 1;
# 四、比较运算符
| 符号 | 描述 |
|---|
BETWEEN | 在两值之间 |
NOT BETWEEN | 不在两值之间 |
IN | 在集合中 |
NOT IN | 不在集合中 |
LIKE | 模糊匹配 |
SELECT * FROM `article` WHERE `id` BETWEEN 1 AND 10;
SELECT * FROM `article` WHERE `id` NOT BETWEEN 1 AND 5;
SELECT * FROM `article` WHERE `id` IN (1,5);
SELECT * FROM `article` WHERE `id` NOT IN (1,5);
SELECT * FROM `article` WHERE `title` LIKE '%PHP%';
SELECT * FROM `article` WHERE `title` LIKE '%PHP_';
