学习mysql

docs/MySQL/mysql是怎样使用的.md

@@ -432,11 +432,11 @@ FROM
     student_info;
 ```
 
-### 7.4 查询所有列
+## 7.4 查询所有列
 
 - 方法：`SELECT * FROM student_info;`
 
-### 7.5 查询结果去重
+## 7.5 查询结果去重
 
 - 方法：`SELECT DISTINCT department[, 列名] FROM student_info`
 
@@ -445,18 +445,72 @@ SELECT DISTINCT department FROM student_info;
 SELECT DISTINCT department, major FROM student_info;
 ```
 
-### 7.6 限制结果集合记录条数（分页）
+## 7.6 限制结果集合记录条数（分页）
 
 - 方法：`SELECT * FROM table_name LIMIT [起始下标, ]搜寻条数`
 
+注意:
+
+- LIMIT一般放在最后
+
 ```sql
-# 查询前两条
+-- 查询前两条
 SELECT * FROM student_info LIMIT 2;
-# 查询两条，从5+1开始
+-- 查询两条，从5+1开始
 SELECT * FROM student_info LIMIT 5, 2;
 ```
 
+## 7.7 对查询结果排序
+
+### 7.7.1 单列查询
+
+- 方法：`ORDER BY 列名 [ASC|DESC]`
+
+ASC为默认升序，DESC为倒序
+
+```sql
+SELECT student_info.number FROM student_info ORDER BY student_info.number ASC;
+SELECT * FROM student_info ORDER BY student_info.number ASC;
+SELECT * FROM student_info ORDER BY student_info.number DESC;
+```
+
+### 7.7.2 多列查询
+
+- 方法：`ORDER BY 列1 [ASC|DESC], 列2 [ASC|DESC],...`
+
+# 第八章 带搜索条件的查询
+
+## 8.1 简单搜索条件
+
+| 运算符 | 示例          | 描述           |
+|-------|-------------|--------------|
+|=| a = b       |              |
+|<=>| a <=> b     | 相等，NULL值安全相等 |
+|<>或!=| a<>b 或 a!=b | 不等           |
+|<|             | 小于           |
+|<=|             | 小于等于         |
+|>|             | 大于           |
+|>=|             | 大于等于         |
+|BETWEEN| a BETWEEN b AND C| a 属于[b, c]|
+|NOT BETWEEN|a NOT BETWEEN b AND C| a 不属于[b, c]|
+
+```sql
+-- 查id等于20210101的学生的所有成绩
+SELECT * FROM student_score WHERE number = 20210101;
+-- 查看除了这个学生的其他的学生的成绩
+SELECT * FROM student_score WHERE number != 20210101;
+SELECT * FROM student_score WHERE number <> 20210101;
+-- 查成绩及格
+SELECT * FROM student_score WHERE score >= 60;
+-- 查成绩不及格
+SELECT * FROM student_score WHERE score < 60;
+-- 查成绩在60到80之间的成绩
+SELECT * FROM student_score WHERE score BETWEEN 60 AND 80;
+-- 查成绩不在60到80之间的成绩
+SELECT * FROM student_score WHERE score NOT BETWEEN 60 AND 80;
+```
 
+## 8.2 匹配列表中的元素 IN