diff --git "a/37 \346\217\255\351\230\263\344\270\275/20231013  \347\252\227\345\217\243\345\207\275\346\225\260 \347\254\224\350\256\260.md" "b/37 \346\217\255\351\230\263\344\270\275/20231013  \347\252\227\345\217\243\345\207\275\346\225\260 \347\254\224\350\256\260.md"
new file mode 100644
index 0000000000000000000000000000000000000000..e177a8f6a5d13936f04670ff2abc189932a5c0ab
--- /dev/null
+++ "b/37 \346\217\255\351\230\263\344\270\275/20231013  \347\252\227\345\217\243\345\207\275\346\225\260 \347\254\224\350\256\260.md"	
@@ -0,0 +1,313 @@
+# 函数复习
+
+### 数学函数
+
+```sql
+-- 绝对值abs()
+select abs(-4) -- 4
+
+-- 向上取整 ceil(值)
+select ceil(1.5) -- 2
+
+-- 向下取整 floor(值)
+select floor(1.5) -- 1
+
+-- 随机数 rand()
+select floor(rand()*100)
+
+-- 四舍五入，截取 round(值，保留点后n位)
+select round(1.6666);
+select round(1.6666,2);
+
+-- 截取 truncate(值,保留点后n位)
+
+```
+
+
+
+### 字符串函数
+
+```sql
+-- 字符个数
+select char_length('abc') -- 3
+select char_length('软件工程') -- 4
+
+-- 拼接字符串
+select concat('你','好','帅哥')
+select concat_ws(',','你','好','帅哥') -- 第一个字符为分隔符
+
+-- 去空
+select ltrim('           aaa');
+select rtrim('aaa           ');
+select trim('         aaa        ')
+
+-- 截取
+select substr('hello',2,3);
+
+-- 获取子串在字符串的位置
+select position('a' in 'abc');
+
+-- 替换 
+select replace('aaabbbccc','a','1');
+
+```
+
+
+
+### 日期函数
+
+```sql
+-- 获取当前日期
+select curdate();
+
+-- 获取当前时间
+select curtime();
+
+-- 获取当前日期时间
+select now();
+
+-- 从日期字符串获取日期
+select date('2000-02-02');
+select date('2000-02-02 12:12:12'); -- 只获取日期
+
+-- 天数差
+select datediff('2001-02-02','2000-02-02'); -- 前减后
+
+-- 指定差
+select timestampdiff(day,'2001-02-02','2000-02-02'); -- 后减前
+
+-- 日期减法
+select subdate('2001-02-02',interval 2 day);
+
+-- 日期加法
+select adddate('2001-02-02',interval 2 day);
+
+-- 获取某日期中的值
+select year('2001-02-02');
+select day('2001-02-02');
+select dayofyear('2001-02-02');
+select dayofweek('2001-02-02');
+
+-- 获取该月最后一天
+select last_day('2001-02-02');
+
+-- 日期格式
+select date_format('2001-02-02','%Y')
+
+```
+
+http://www.manongjc.com/detail/29-ensoneygersabbx.html
+
+
+
+# 控制流函数
+
+```sql
+-- if(表达式,值1,值2)  true返回值1，false返回值2
+select if(1<2,1,2);
+
+-- ifnull(值1，值2) 如果值1不为null，返回值1，否则返回值2
+select ifnull(null,2);
+select ifnull(1,2);
+
+-- isnull(表达式) 返回1或0
+select isnull(null);
+select isnull('');
+
+-- nullif(值1，值2) 比较两个值（字符串）,如果当等返回null，否则返回值1
+select nullif(25,25);
+```
+
+```sql
+-- case when 
+/*
+语法1：
+case
+	when 条件表达式1 then 值1
+	when 条件表达式2 then 值2
+	...
+	else 值n
+end
+
+语法2：
+case 表达式
+	when 条件值1 then 返回值1
+	when 条件值2 then 返回值2
+	...
+	else 返回值n
+end
+
+*/
+```
+
+
+
+# 窗口函数
+
+mysql 8.0新增窗口函数（开窗函数）。
+
+非聚合窗口函数：是相对于聚合函数来说的，特性为非聚合。一次只处理一行数据。
+
+窗口聚合函数：窗口聚合函数在单元行上计算某个字段的结果时，可将窗口范围内的数据输入到聚合函数中，并且不会改变行数。
+
+
+
+### 语法
+
+```sql
+窗口函数名称(参数) over(partition by ... order by... 窗口大小)
+```
+
+partition by 分组,等价于group by
+
+order by 排序
+
+
+
+### 序号函数
+
+row_number()、rank()、dense_rank()
+
+
+
+### 开窗聚合函数 
+
+```sql
+sum()|avg()|min()|max()|count()| over (partition by ... order by...)
+```
+
+案例:
+
+```sql
+# 获取各部门薪金总和(合计)
+select ename,hiredate,deptno,sal,
+sum(sal) over(partition by deptno) 'sum'
+from emp;
+
+# 获取各部门薪金总和(累加)
+select ename,hiredate,deptno,sal,
+sum(sal) over(partition by deptno order by sal) 'sum'
+from emp;
+```
+
+
+
+#### 窗口大小
+
+```sql
+# 开窗范围
+# 获取各部门薪金总和(范围：初始行至当前行)
+select ename,hiredate,deptno,sal,
+sum(sal) over(partition by deptno rows between unbounded preceding and current row) 'sum'
+from emp;
+
+-- rows 启用窗口大小
+-- between ... and ... 范围区间
+-- unbounded preceding 起始行
+-- current row 当前行
+```
+
+不同案例：
+
+```sql
+# 范围：前3行 + 当前行
+sum(sal) over(partition by deptno rows between 3 preceding and current row)
+
+# 范围：前3行 + 当前行 + 后1行
+sum(sal) over(partition by deptno rows between 3 preceding and 1 following) 
+-- following指当前行之后的行
+
+# 范围：当前行至最后一行
+sum(sal) over(partition by deptno rows between current row and unbounded following) 
+-- unbounded following 最终行
+```
+
+
+
+### 分布函数
+
+##### cume_dist()
+
+分组内 <= 或 >= 当前值的行数占比(包含当前值本身)
+
+```sql
+# 查询各部门员工小于等于当前薪资的比例
+
+select ename,deptno,sal,
+cume_dist() over(partition by deptno order by sal) '占比'
+from emp;
+
+-- order by 控制计算的列
+-- asc 小于等于
+-- desc 大于等于
+```
+
+
+
+### 前后函数
+
+返回当前行的前某一行的值，或者后某一行的值
+
+lag(列名，前第n行) 
+
+lead(列名，后第n行) 
+
+```sql
+select ename,deptno,sal,
+lag(sal,1) over(partition by deptno order by sal) '前1',
+lag(sal,2) over(partition by deptno order by sal) '前2'
+from emp;
+```
+
+
+
+### 头尾函数
+
+返回第一个或最后一个列的值
+
+first_value(列名)
+
+last_value(列名)
+
+```sql
+-- 查询各个部门中，第一个和最后一个入职的员工姓名
+select ename,deptno,sal,hiredate,
+first_value(ename) over(partition by deptno order by hiredate) 'first',
+last_value(ename) over(partition by deptno order by hiredate) 'last'
+from emp;
+```
+
+
+
+### 其他函数
+
+nth_value(列名,n) —— 返回截止到当前行，该列的第n个值
+
+```sql
+-- 查找出各个部门，薪资排名第2的员工姓名
+select ename,deptno,sal,
+nth_value(ename) over(partition by deptno order by sal) '第二名'
+from emp;
+
+-- 查询全公司，薪资排名第2的员工姓名
+-- 1
+select ename,deptno,sal,
+nth_value(ename,2) over(order by sal) '第二名'
+from emp;
+-- 2
+select ename,deptno,sal,
+nth_value(ename,2) over() '第二名'
+from emp order by sal;
+```
+
+ntile(n) —— 将分区中的有序数据分为n个等级，记录等级数
+
+```sql
+-- 将每个部门员工按照入职日期分成3组
+select ename,deptno,sal,
+ntile(3) over(partition by deptno order by hiredate) '组别'
+from emp;
+
+-- 找出每个部门中的老员工？？
+```
+
diff --git "a/37 \346\217\255\351\230\263\344\270\275/20231013  \347\252\227\345\217\243\345\207\275\346\225\260.md" "b/37 \346\217\255\351\230\263\344\270\275/20231013  \347\252\227\345\217\243\345\207\275\346\225\260.md"
new file mode 100644
index 0000000000000000000000000000000000000000..32b781ee12cc0b05a0b0517defba3281c6cc8245
--- /dev/null
+++ "b/37 \346\217\255\351\230\263\344\270\275/20231013  \347\252\227\345\217\243\345\207\275\346\225\260.md"	
@@ -0,0 +1,332 @@
+## 课后练习
+
+```sql
+CREATE DATABASE uu charset utf8;
+use uu;
+
+create table if not exists `employee`
+(
+    `eid` int not null auto_increment comment '员工id' primary key,
+    `ename` varchar(20) not null comment '员工名称',
+    `dname` varchar(50) not null comment '部门名称',
+    `hiredate` datetime not null comment '入职日期',
+		`birth` date not null comment '生日',
+    `salary` double null comment '基本薪资',
+		`start_sal` double null comment '入职薪资'
+);
+
+insert into `employee` (`ename`, `dname`, `hiredate`,`birth`, `salary`,`start_sal`) values ('傅嘉熙', '开发部', '2002-08-20 12:00:04','1980-12-10', 9000,6500);
+insert into `employee` (`ename`, `dname`, `hiredate`, `birth`,`salary`,`start_sal`) values ('武晟睿', '开发部', '2002-06-12 13:54:12', '1984-2-5',9500,6000);
+insert into `employee` (`ename`, `dname`, `hiredate`, `birth`,`salary`,`start_sal`) values ('孙弘文', '开发部', '2003-10-16 08:27:06','1979-8-7', 9400,8000);
+insert into `employee` (`ename`, `dname`, `hiredate`,`birth`, `salary`,`start_sal`) values ('潘乐驹', '开发部', '2004-04-22 03:56:11','1980-5-12', 9500,6800);
+insert into `employee` (`ename`, `dname`, `hiredate`,`birth`, `salary`,`start_sal`) values ('潘昊焱', '人事部', '2007-02-24 03:40:02','1987-2-12', 5000,4500);
+insert into `employee` (`ename`, `dname`, `hiredate`,`birth`, `salary`,`start_sal`) values ('沈涛', '人事部', '2012-12-14 09:16:37','1993-4-30', 6000,5500);
+insert into `employee` (`ename`, `dname`, `hiredate`, `birth`,`salary`,`start_sal`) values ('江峻熙', '人事部', '2018-05-12 01:17:48','1990-6-8', 5000,3000);
+insert into `employee` (`ename`, `dname`, `hiredate`,`birth`, `salary`,`start_sal`) values ('陆远航', '人事部', '2018-04-14 03:35:57','1989-11-13', 5500,5000);
+insert into `employee` (`ename`, `dname`, `hiredate`, `birth`,`salary`,`start_sal`) values ('姜煜祺', '销售部', '2020-03-23 03:21:05','1995-1-1', 6000,5500);
+insert into `employee` (`ename`, `dname`, `hiredate`, `birth`,`salary`,`start_sal`) values ('邹明', '销售部', '2015-11-23 23:10:06','1996-2-19', 6800,6000);
+insert into `employee` (`ename`, `dname`, `hiredate`, `birth`,`salary`,`start_sal`) values ('董擎苍', '销售部', '2012-02-12 07:54:32','1985-10-7', 6500,4800);
+insert into `employee` (`ename`, `dname`, `hiredate`,`birth`, `salary`,`start_sal`) values ('钟俊驰', '销售部', '2010-04-10 12:17:06','1981-3-25', 6000,3500);
+```
+
+```sql
+-- 员工按工龄，每年增加50元薪水。实发薪资 = 基本薪资 + 工龄 * 50
+
+
+### -- 窗口函数
+
+select * from employee;
+
+#求每个部门的员工总数
+
+SELECT DISTINCT
+	dname 部门,
+	COUNT( ename ) over ( PARTITION BY dname ) 员工总数 
+FROM
+	employee;
+
+
+#求每个部门的平均工资
+
+SELECT DISTINCT
+	dname 部门,
+	AVG( salary ) over ( PARTITION BY dname ) 平均薪资 
+FROM
+	employee;
+#求每个部门的工资排名（从高到低,相同工资并列，并执行跳过排序）
+
+SELECT DISTINCT
+  dname 部门,
+	ename 姓名,
+	salary 工资,
+	rank() over ( PARTITION BY dname ORDER BY salary desc ) 平均薪资 
+FROM
+	employee ;
+#求公司所有员工的年龄排序（相同年龄并列，执行跳过排序）
+
+SELECT
+	ename 姓名,
+	birth 生日,
+	RANK() over ( ORDER BY birth DESC ) 排名 
+FROM
+	employee;
+
+
+#求每个部门的员工工龄排序（相同年龄并列，执行顺序排序）
+SELECT
+	ename 姓名,
+	hiredate 工龄,
+	DENSE_RANK() over ( ORDER BY hiredate DESC ) 排名 
+FROM
+	employee;
+
+#计算每个员工的工资与该部门平均工资的差额
+SELECT
+	ename 员工,
+	dname 部门,
+	salary 工资,
+	AVG( salary ) over ( PARTITION BY dname )- salary 
+FROM
+	employee;
+	
+#按员工工资进行排序，比较相邻两个员工的工资，输出比较高的工资
+SELECT
+	ename,
+	salary `工资`,
+	MAX( salary ) over ( rows BETWEEN 1 preceding AND 1 following ) 较高的工资 
+FROM
+	employee;
+#按员工工资进行排序，查询当前员工与前一位和后一位的工资平均值
+SELECT
+	ename,
+	salary 工资,
+	TRUNCATE (
+		avg( salary ) over ( rows BETWEEN 1 preceding AND 1 following ),
+		0 
+	) 前一位和后一位的工资平均值 
+FROM
+	employee;
+#按员工工资进行排序，查询当前员工至最后一位员工的工资总和
+SELECT
+	ename,
+	salary,
+	sum( salary ) over ( rows BETWEEN current ROW AND unbounded following ) 至最后一位员工的工资总和 
+FROM
+	employee;
+#计算每个部门内最高薪资与平均薪资的差额
+SELECT DISTINCT
+	dname,
+	max( salary ) over ( PARTITION BY dname )- avg( salary ) over ( PARTITION BY dname ) 最高薪资与平均薪资的差额 
+FROM
+	employee;
+#找出各部门年薪第二高的员工
+SELECT
+	* 
+FROM
+	(
+	SELECT
+		ename,
+		dname,
+		salary,
+		dense_RANK() over ( PARTITION BY dname ORDER BY salary ) `ranks` 
+	FROM
+		employee 
+	) r 
+WHERE
+	ranks = 2;
+#查询各部门中小于等于当前员工实际薪资的比例
+SELECT
+	dname,
+	ename,
+	salary,
+	cume_dist() over ( PARTITION BY dname ORDER BY salary ASC ) 
+FROM
+	employee;
+#查询每个员工工资在全部员工中的排名比例
+SELECT
+	RANK() OVER w,
+	ename,
+	salary,
+	TRUNCATE ( PERCENT_RANK() over w, 2 ) 
+FROM
+	employee window w AS ( ORDER BY salary DESC );
+#查询每个部门工资排名在前25%的员工记录数
+SELECT
+	* 
+FROM
+	(
+	SELECT
+		dname,
+		ename,
+		salary,
+		TRUNCATE (
+			PERCENT_RANK() over ( PARTITION BY dname ORDER BY salary ),
+			2 
+		) 工资比例 
+	FROM
+		employee 
+	) p 
+WHERE
+	工资比例 >= 0.25;
+#每个部门按年龄进行排序，求当前员工与前一位员工的年龄差
+SELECT
+	ename,
+	dname,
+	birth,
+	TRUNCATE (
+		DATEDIFF(
+			NOW(),
+		LAG( birth, 1 ) over ( PARTITION BY dname ))/ 365,
+		0 
+	) 当前员工与前一位员工的年龄差 
+FROM
+	employee;
+#按入职日期进行排序，查询公司每个员工与后面一个员工的入职天数差异
+SELECT
+	ename,
+	hiredate,
+	DATEDIFF(
+		hiredate,
+	lead( hiredate, 1 ) over ()) 
+FROM
+	employee;
+#将每个部门的员工按工资平均分为2个组，组1为低工资，组2为高工资
+SELECT
+	ntile( 2 ) over ( PARTITION BY dname ORDER BY salary ) 组,
+	ename,
+	dname,
+	salary 
+FROM
+	employee;
+#将所有员工按照工龄分为4个组，并统计每个组的人数
+SELECT
+	a.*,
+	COUNT(组别) over ( PARTITION BY 组别 ) 每个组的人数 
+FROM
+	(
+	SELECT
+		ename,
+		hiredate,
+		TRUNCATE (( DATEDIFF( NOW(), birth )/ 365 ), 0 ) 工龄,
+		NTILE( 4 ) over (
+			
+		ORDER BY
+		( DATEDIFF( NOW(), birth )/ 365 )) `组别` 
+	FROM
+		employee 
+	) a;
+#将员工按照工资分为3个组，并统计组别，每组平均工资，工资范围（first_value、last_value）
+SELECT
+	a.*,
+	AVG( salary ) over w 每组平均工资,
+	first_value( salary ) over w,
+	last_value( salary ) over w 
+FROM
+	(
+	SELECT
+		ename,
+		salary,
+		NTILE( 3 ) over ( ORDER BY salary ) 组别 
+	FROM
+		employee 
+	) a window w AS ( PARTITION BY a.组别 );### -- 非窗口函数
+#按照工龄区分等级，小于5年为新员工,5-15年为老员工,大于15年为骨灰级员工,输出姓名，部门，工龄，级别
+SELECT
+	t.*,
+CASE
+		
+		WHEN t.`工龄` < 5 THEN
+		'新员工' 
+		WHEN t.`工龄` BETWEEN 5 
+		AND 15 THEN
+			'老员工' ELSE '骨灰级员工' 
+		END 级别 
+FROM
+	(
+	SELECT
+		ename,
+		dname,
+		hiredate,
+		TRUNCATE (( DATEDIFF( NOW(), birth )/ 365 ), 0 ) 工龄 
+	FROM
+		employee 
+	) t;
+#返回员工的实际年龄，如果小于当前日期则减1岁
+SELECT
+	ename,
+	hiredate,(
+		YEAR (
+		NOW())- YEAR ( birth ))-
+CASE
+		
+		WHEN date_format( NOW(), '%m%d' )> DATE_FORMAT( birth, '%m%d' ) THEN
+		0 ELSE 1 
+	END 年龄 
+FROM
+	employee;
+#求每个员工还有多少天过生日，并返回下次生日是星期几
+SELECT
+	ename,
+	CONCAT_WS( '-', MONTH ( birth ), DAY ( birth ) ) 生日,
+	DATEDIFF(
+		CURRENT_DATE (),
+		CONCAT_WS(
+			'-',
+			YEAR ( CURRENT_DATE ),
+			MONTH ( birth ),
+			DAY ( birth ) 
+		) 
+	) 距离下次生日的天数,
+CASE
+		DATE_FORMAT(
+			CONCAT_WS(
+				'-',
+			CASE
+					
+					WHEN DATEDIFF(
+						CURRENT_DATE (),
+						CONCAT_WS(
+							'-',
+							YEAR ( CURRENT_DATE ),
+							MONTH ( birth ),
+							DAY ( birth ) 
+						) 
+						) > 0 THEN
+						YEAR ( CURRENT_DATE )+ 1 ELSE YEAR ( CURRENT_DATE ) 
+					END,
+					MONTH ( birth ),
+					DAY ( birth ) 
+				),
+				'%w' 
+			) 
+			WHEN 0 THEN
+			'周日' 
+			WHEN 1 THEN
+			'周一' 
+			WHEN 2 THEN
+			'周二' 
+			WHEN 3 THEN
+			'周三' 
+			WHEN 4 THEN
+			'周四' 
+			WHEN 5 THEN
+			'周五' 
+			WHEN 6 THEN
+			'周六' 
+		END 下次生日的星期 
+FROM
+	employee;
+#求每个员工当前实发工资与入职时工资的增长率,输出员工姓名,部门,入职工资,实际工资,增长率
+SELECT
+	ename,
+	dname,
+	start_sal,
+	salary,
+	CONCAT(
+		format(( salary - start_sal )/ start_sal * 100, 2 ),
+		'%' 
+	) 
+FROM
+	employee;
+```
+