diff --git "a/49 \346\235\216\350\210\222\346\261\266/10.19\344\272\213\345\212\241.md" "b/49 \346\235\216\350\210\222\346\261\266/10.19\344\272\213\345\212\241.md"
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@@ -0,0 +1,178 @@
+## 事务
+
+### 事务的特性
+
+```sql
+原子性、一致性、隔离性、持久性
+```
+
+### 事务操作
+
+```sql
+mysql中事务默认是隐式事务，执行insert、update、delete操作的时候，数据库自动开启事务、提交或回滚事务
+
+是否开启隐式事务是由变量autocommit控制的
+
+所以事务分为**隐式事务**和**显式事务
+```
+
+#### 隐式事务
+
+```sql
+事务自动开启、提交或回滚，比如insert、update、delete语句，事务的开启、提交或回滚由mysql内部自动控制的。
+
+查看变量autocommit是否开启了自动提交
+```
+
+#### 显式事务
+
+事务需要手动开启、提交或回滚，由开发者自己控制。
+
+```mysql
+-- 显示所有的系统变量
+show variables;
+
+-- 查看autocommit状态
+show variables like 'autocommit';
+
+-- 显式事务（手动提交，关闭系统自动）
+set autocommit=off;
+set autocommit=0;
+
+rollback; -- 撤销，可以保留数据
+commit; -- 提交数据
+
+-- 隐式事务（自动提交，开启系统自动）
+set autocommit=on;
+set autocommit=1;
+
+rollback; -- 撤销，不保留数据，因为系统已经自动commit
+```
+
+```mysql
+-- 开启事务
+start transaction;
+-- 结束事务
+rollback / commit;
+```
+
+### savepoint关键字
+
+可以将一大批操作分为几个部分，然后指定回滚某个部分。
+
+```mysql
+-- 在事务中途使用
+savepoint 保存名;
+
+-- 追溯回去
+rollback to 保存名;
+```
+
+### 只读事务
+
+表示在事务中执行的是一些只读操作，如查询，但是不会做insert、update、delete操作，数据库内部对只读事务可能会有一些性能上的优化
+
+```mysql
+start transaction read only;
+```
+
+#### 脏读
+
+读已提交可重复读
+
+#### 幻读
+
+### 隔离级别
+
+隔离级别分为4种：
+
+```mysql
+读未提交：READ-UNCOMMITTED
+读已提交：READ-COMMITTED
+可重复读：REPEATABLE-READ
+串行：SERIALIZABLE
+```
+
+
+
+## 作业
+
+```mysql
+-- 部门表
+create table dept(
+    deptno int primary key auto_increment, -- 部门编号
+    dname varchar(14) ,      -- 部门名字
+    loc varchar(13)   -- 地址
+) ;
+-- 员工表
+create table emp(
+    empno int primary key auto_increment,-- 员工编号
+    ename varchar(10), -- 员工姓名                                        -
+    job varchar(9),    -- 岗位
+    mgr int,     -- 直接领导编号
+    hiredate date, -- 雇佣日期，入职日期
+    sal int, -- 薪水
+    comm int,  -- 提成
+    deptno int not null, -- 部门编号
+    foreign key (deptno) references dept(deptno)
+);
+insert into dept values(10,'财务部','北京');
+insert into dept values(20,'研发部','上海');
+insert into dept values(30,'销售部','广州');
+insert into dept values(40,'行政部','深圳');
+insert into emp values(7369,'刘一','职员',7902,'1980-12-17',800,null,20);
+insert into emp values(7499,'陈二','推销员',7698,'1981-02-20',1600,300,30);
+insert into emp values(7521,'张三','推销员',7698,'1981-02-22',1250,500,30);
+insert into emp values(7566,'李四','经理',7839,'1981-04-02',2975,null,20);
+insert into emp values(7654,'王五','推销员',7698,'1981-09-28',1250,1400,30);
+insert into emp values(7698,'赵六','经理',7839,'1981-05-01',2850,null,30);
+insert into emp values(7782,'孙七','经理',7839,'1981-06-09',2450,null,10);
+insert into emp values(7788,'周八','分析师',7566,'1987-06-13',3000,null,20);
+insert into emp values(7839,'吴九','总裁',null,'1981-11-17',5000,null,10);
+insert into emp values(7844,'郑十','推销员',7698,'1981-09-08',1500,0,30);
+insert into emp values(7876,'郭十一','职员',7788,'1987-06-13',1100,null,20);
+insert into emp values(7900,'钱多多','职员',7698,'1981-12-03',950,null,30);
+insert into emp values(7902,'大锦鲤','分析师',7566,'1981-12-03',3000,null,20);
+insert into emp values(7934,'木有钱','职员',7782,'1983-01-23',1300,null,10);
+
+
+
+-- 1、列出最低薪金大于1500的各种工作。
+select job from emp group by job having min(sal)>1500;
+
+-- 2、列出在部门 "销售部" 工作的员工的姓名，假定不知道销售部的部门编号。
+select ename from emp,dept where dname='销售部';
+
+-- 3、列出薪金高于公司平均薪金的所有员工。
+select ename,sal from emp where sal>(select avg(sal) from emp);
+
+-- 4、列出与"周八"从事相同工作的所有员工。
+select ename,job from emp where job=(select job from emp where ename='周八');
+
+-- 5、列出薪金等于部门30中员工的薪金的所有员工的姓名和薪金。
+select ename,sal from emp where sal in (select distinct sal from emp where deptno=30);
+
+-- 6、列出薪金高于在部门30工作的所有员工的薪金的员工姓名和薪金。
+select ename,sal from emp where sal > (select max(sal) from emp where deptno=30);
+
+-- 7、列出在每个部门工作的员工数量、平均工资、平均服务年限。
+select count(empno) 员工数量,avg(sal) 平均工资,avg(datediff(now(),hiredate)) div 365 平均服务年限 from emp group by deptno;
+
+-- 8、列出所有员工的姓名、部门名称和工资。
+select ename,dname,sal from emp e join dept d on e.deptno=d.deptno;
+
+-- 9、列出所有部门的详细信息和部门人数。
+select count(empno) 部门人数,d.* from emp e left join dept d on e.deptno=d.deptno group by deptno;
+
+-- 10、列出各种工作的最低工资。
+select job,min(sal) over (partition by job) 最低工资 from emp;
+
+select job,min(sal) from emp group by job;
+
+-- 11、列出各个部门的 经理 的最低薪金。
+select min(sal) 最低薪金 from emp where job='经理' group by deptno;
+
+-- 12、列出所有员工的年工资,按年薪从低到高排序。 
+select ename,sal*12 from emp order by sal*12;
+
+```
diff --git "a/49 \346\235\216\350\210\222\346\261\266/\345\244\215\344\271\24050\351\242\230.md" "b/49 \346\235\216\350\210\222\346\261\266/\345\244\215\344\271\24050\351\242\230.md"
new file mode 100644
index 0000000000000000000000000000000000000000..01483ec05424d14f63c9f041f3ccf2764fabbe19
--- /dev/null
+++ "b/49 \346\235\216\350\210\222\346\261\266/\345\244\215\344\271\24050\351\242\230.md"	
@@ -0,0 +1,464 @@
+```sql
+# 学生表
+CREATE TABLE IF NOT EXISTS `student`(
+    `student_id` INT(10) NOT NULL AUTO_INCREMENT COMMENT '学号',
+    `student_name` VARCHAR(10) NOT NULL DEFAULT '匿名' COMMENT '姓名',
+    `birthday` DATETIME NOT NULL COMMENT '出生日期',
+    `gender` VARCHAR(10) NOT NULL DEFAULT '男' COMMENT '性别',
+    PRIMARY KEY(`student_id`)
+)ENGINE=INNODB CHARSET=utf8;
+
+INSERT INTO `student` VALUES
+(1 , '赵雷' , '1990-01-01' , '男'),
+(2 , '钱电' , '1990-12-21' , '男'),
+(3 , '孙风' , '1990-12-20' , '男'),
+(4 , '李云' , '1990-12-06' , '男'),
+(5 , '周梅' , '1991-12-01' , '女'),
+(6 , '吴兰' , '1992-01-01' , '女'),
+(7 , '郑竹' , '1989-01-01' , '女'),
+(8 , '张三' , '2017-12-20' , '女'),
+(9 , '李四' , '2017-12-25' , '女'),
+(10 , '李四' , '2012-06-06' , '女'),
+(11 , '赵六' , '2013-06-13' , '女'),
+(12 , '孙七' , '2014-06-01' , '女');
+-- 课程表
+CREATE TABLE IF NOT EXISTS `course`(
+    `course_id` INT(4) NOT NULL AUTO_INCREMENT COMMENT '课程编号',
+    `course_name` VARCHAR(10) NOT NULL COMMENT '课程名',
+    `teacher_id` INT(10) NOT NULL COMMENT '任课教师工号',
+    PRIMARY KEY(`course_id`)
+)ENGINE=INNODB CHARSET=utf8;
+
+INSERT INTO `course` VALUES
+(1, '语文', 2),
+(2, '数学', 1),
+(3, '英语', 3);
+# 教师表
+CREATE TABLE IF NOT EXISTS `teacher`(
+    `teacher_id` INT(10) NOT NULL AUTO_INCREMENT COMMENT '教师工号',
+    `teacher_name` VARCHAR(10) NOT NULL DEFAULT '匿名' COMMENT '教师姓名',
+    PRIMARY KEY(`teacher_id`)
+)ENGINE=INNODB CHARSET=utf8;
+
+INSERT INTO `teacher` VALUES
+(1, '高斯'),
+(2, '李白'),
+(3, 'Trump');
+
+-- 成绩表
+CREATE TABLE IF NOT EXISTS `score`(
+    `student_id` INT(10) NOT NULL COMMENT '学号',
+    `course_id` INT(4) NOT NULL COMMENT '课程编号',
+    `score` DECIMAL(18,1) COMMENT '成绩',
+    KEY(`course_id`)
+)ENGINE=INNODB CHARSET=utf8;
+
+INSERT INTO `score` VALUES
+(1 , 1 , 80),
+(1 , 2 , 90),
+(1 , 3 , 99),
+(2 , 1 , 70),
+(2 , 2 , 60),
+(2 , 3 , 80),
+(3 , 1 , 80),
+(3 , 2 , 80),
+(3 , 3 , 80),
+(4 , 1 , 50),
+(4 , 2 , 30),
+(4 , 3 , 20),
+(5 , 1 , 76),
+(5 , 2 , 87),
+(6 , 1 , 31),
+(6 , 3 , 34),
+(7 , 2 , 89),
+(7 , 3 , 98);
+
+
+```
+
+## 题目：
+
+1. 查询" 1 "课程比" 2 "课程成绩高的学生的信息（学号、姓名、性别、出生日期）及课程分数
+   
+   ```mysql
+   select s.* from
+   student s,
+   (select * from score where course_id='1') a,
+   (select * from score where course_id='2') b
+   where a.score>b.score
+   and a.student_id=b.student_id
+   and b.student_id=s.student_id;
+   ```
+   
+   ```mysql
+   select s1.*,s2.course_id,s2.score from student s1 left join score s2 on s1.student_id=s2.student_id where s2.course_id!=3 and s1.student_id in 
+       (select a.student_id from 
+           (select * from score where course_id=1) a,
+           (select * from score where course_id=2) b 
+       where a.score>b.score and a.student_id=b.student_id);
+   ```
+
+2. 查询同时参与" 1 "课程和" 2 "课程考试的学生信息
+   
+   ```mysql
+   select * from student where student_id in 
+       (select a.student_id from 
+           (select * from score where course_id=1) a,
+           (select * from score where course_id=2) b 
+   where a.student_id=b.student_id);
+   ```
+
+3. 查询存在" 1 "课程但可能不存在" 2 "课程的情况(不存在时显示为 null )
+   
+   ```mysql
+   select ifnull(s1.student_id,'null'),ifnull(s1.course_id,'null'),ifnull(s1.score,'null'),s2.* from 
+       (select * from score where course_id=1) s1 
+       right join 
+       (select * from score where course_id=2) s2 
+   on s1.student_id=s2.student_id;
+   ```
+
+4. 查询不存在" 1 "课程但存在" 2 "课程的情况
+   
+   ```mysql
+   select * from score where student_id not in (select student_id from score where course_id=1);
+   
+   select ifnull(s2.student_id,'null'),ifnull(s2.course_id,'null'),ifnull(s2.score,'null'),s1.* from 
+       (select * from score where course_id=1) s1 
+       left join 
+       (select * from score where course_id=2) s2 
+   on s1.student_id=s2.student_id;
+   ```
+
+5. 查询平均成绩大于等于 60 分的同学的学生编号、姓名和平均成绩
+   
+   ```mysql
+   select s1.student_id,s2.student_name,round(avg(score)) from score s1 left join student s2 on s1.student_id=s2.student_id group by student_id having avg(score)>=60;
+   ```
+
+6. 查询在成绩表存在成绩的学生信息
+   
+   ```mysql
+   select * from student where student_id in (select student_id from score);
+   ```
+
+7. 查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩(没成绩的显示为 null )
+   
+   ```mysql
+   select s1.student_id,s1.student_name,count(s2.course_id),ifnull(sum(s2.score),'null') from student s1 left join score s2 on s1.student_id=s2.student_id group by s1.student_id;
+   ```
+
+8. 查询「李」姓老师的数量
+   
+   ```mysql
+   select count(teacher_id) from teacher where teacher_name like '李%';
+   ```
+
+9. 查询学过「李白」老师授课的同学的信息
+   
+   ```mysql
+   select * from student where student_id in (select student_id from score where course_id in (select course_id from course where teacher_id in (select teacher_id from teacher where teacher_name='李白')));
+   ```
+
+10. 查询没有学全所有课程的同学的信息
+    
+    ```mysql
+    select s2.*,count(s1.course_id) from score s1 right join student s2 on s1.student_id=s2.student_id group by s2.student_id having count(s1.course_id)<(select count(*) from course);
+    ```
+
+11. 查询至少有一门课与学号为" 1 "的同学所学相同的同学的信息
+    
+    ```mysql
+    select * from student where student_id in (select student_id from score where course_id in (select course_id from score where student_id=1) and student_id!=1);
+    ```
+
+12. 查询和" 1 "号的同学学习的课程完全相同的其他同学的信息
+    
+    ```mysql
+    select student_id,student_name,course_id from student s,(select 
+    select *
+    from student 
+    where student.student_id not in (
+    select *
+    from 
+    (select student.student_id,a.course_id
+    from student ,(select course_id from score where student_id='01') as a )as b 
+    left join score  on b.student_id=score.student_id and b.course_id=score.course_id
+    where score.course_id is null )
+    and student.student_id !='01';
+    ```
+    
+    ```mysql
+    select * from student where student_id in (select student_id from score group by Student_id having count(course_id)=(select count(course_id) from score where student_id=1)) and student_id!=1;
+    ```
+    
+    ```mysql
+    select s2.* from score s1 left join student s2 on s1.student_id=s2.student_id where s1.student_id!=1 group by s1.student_id having count(s1.course_id)=(select count(course_id) from score where student_id=1);
+    ```
+    
+    ```mysql
+    select * from student where student_id in(select distinct student_id from score where student_id not in(select student_id from score where course_id not in(select course_id from score where student_id=1)) group by student_id having count(course_id)=(select count(course_id) from score where student_id=1) and student_id!=1);
+    ```
+
+13. 查询没学过「李白」老师讲授的任一门课程的学生姓名
+    
+    ```mysql
+    select student_name from student where student_id not in (select student_id from score where course_id in (select course_id from course where teacher_id=(select teacher_id from teacher where teacher_name='李白')) group by student_id);
+    ```
+    
+    ```mysql
+    select student_name from student 
+    where student_id not in(
+    select student_id from score where course_id in(
+    select course_id from course,teacher
+    where course.teacher_id=teacher.teacher_id and teacher_name='李白'));
+    ```
+
+14. 查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩
+    
+    ```mysql
+    select s1.student_id,s2.student_name,avg(s1.score) from score s1 left join student s2 on s1.student_id=s2.student_id where score<60 group by student_id having count(course_id)>=2;
+    ```
+
+15. 检索" 1 "课程分数小于 60，按分数降序排列的学生信息
+    
+    ```mysql
+    select * from student where student_id in (select student_id from score where course_id=1 and score<60 order by score desc); 
+    ```
+    
+    ```mysql
+    select
+    st.*,
+    sc.score
+    from student st
+    left join score sc 
+    on sc.student_id=st.student_id
+    where sc.course_id=1 and sc.score<60
+    order by sc.score desc ;
+    ```
+
+16. 按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩
+    
+    ```mysql
+    select a.*,s1.course_id,s1.score from score s1 right join (select student_id,avg(score) from score group by student_id order by avg(score) desc) a on s1.student_id=a.student_id;
+    ```
+
+17. 查询各科成绩最高分、最低分和平均分
+    
+    ```mysql
+    select course_id,max(score),min(score),avg(score) from score group by course_id;
+    ```
+
+18. 以如下形式显示：课程 ID，课程 name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率（及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90），要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列
+    
+    ```mysql
+    select a.course_id,max(a.score) 最高分 ,min(a.score) 最低分,avg(a.score) 平均分,
+           ((select count(student_id) from score where score>=60 and course_id=b.course_id )/(select count(student_id) from score where course_id=b.course_id)) 及格率
+    from score a
+    inner join course b on a.course_id = b.course_id
+    group by b.course_id;
+    ```
+
+19. 按各科成绩进行排序，并显示排名，Score 重复时保留名次空缺
+    
+    ```mysql
+    select student_id,course_id,score,rank() over (partition by course_id order by score) from score;
+    ```
+
+20. 按各科成绩进行排序，并显示排名，Score 重复时合并名次
+    
+    ```mysql
+    select student_id,course_id,score,row_number() over (partition by course_id order by score) from score;
+    ```
+
+21. 查询学生的总成绩，并进行排名，总分重复时保留名次空缺
+    
+    ```mysql
+    select a.student_id,rank() over (order by a.score desc) 排名 ,a.score from (select student_id,sum(score) score from score group by student_id) a;
+    ```
+
+22. 查询学生的总成绩，并进行排名，总分重复时不保留名次空缺
+    
+    ```mysql
+    select a.student_id,dense_rank() over (order by a.score desc) 排名 ,a.score from (select student_id,sum(score) score from score group by student_id) a;
+    ```
+
+23. 统计各科成绩各分数段人数：课程编号，课程名称，[100-85]，[85-70]，[70-60]，[60-0] 及所占百分比
+    
+    ```mysql
+    select c.course_id,c.course_name
+    ,((select count(*) from score sc where sc.course_id=c.course_id and sc.score<=100 and sc.score>80)/(select count(*) from score sc where sc.course_id=c.course_id )) "100-85"
+    ,((select count(*) from score sc where sc.course_id=c.course_id and sc.score<=85 and sc.score>70)/(select count(*) from score sc where sc.course_id=c.course_id )) "85-70"
+    ,((select count(*) from score sc where sc.course_id=c.course_id and sc.score<=70 and sc.score>60)/(select count(*) from score sc where sc.course_id=c.course_id )) "70-60"
+    ,((select count(*) from score sc where sc.course_id=c.course_id and sc.score<=60 and sc.score>=0)/(select count(*) from score sc where sc.course_id=c.course_id )) "60-0"
+    from course c order by c.course_id;
+    ```
+
+24. 查询各科成绩前三名的记录
+    
+    ```mysql
+    select * from 
+    (select student_id,score,rank() over (partition by course_id order by score desc) ranks from score) s
+    where ranks<4;
+    ```
+
+25. 查询每门课程被选修的学生数
+    
+    ```mysql
+    select distinct s.course_id,c.course_name,count(s.student_id) over (partition by s.course_id) 学生数 from score s left join course c on s.course_id=c.course_id;
+    ```
+
+26. 查询出只选修两门课程的学生学号和姓名
+    
+    ```mysql
+    select s.student_name 姓名,a.学号 from (select distinct student_id 学号,count(course_id) over (partition by student_id) 选修数 from score) a left join student s on a.`学号`=s.student_id where 选修数=2;
+    ```
+
+27. 查询男生、女生人数
+    
+    ```mysql
+    select gender,count(student_id) from student group by gender;
+    ```
+
+28. 查询名字中含有「风」字的学生信息
+    
+    ```mysql
+    select * from student where student_name like '%风%';
+    ```
+
+29. 查询同名同性学生名单，并统计同名人数
+    
+    ```mysql
+    select student_name from student group by student_name having count(student_id)>1;
+    ```
+
+30. 查询 1990 年出生的学生名单
+    
+    ```mysql
+    select * from student where year(birthday)='1990';
+    ```
+
+31. 查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列
+    
+    ```mysql
+    select course_id,avg(score) from score group by course_id order by avg(score) desc,course_id asc;
+    ```
+
+32. 查询平均成绩大于等于 85 的所有学生的学号、姓名和平均成绩
+    
+    ```mysql
+    select s.student_id,s.student_name,a.`平均成绩` from student s right join (select student_id,avg(score) 平均成绩 from score group by student_id having avg(score)>=85) a on s.student_id=a.student_id;
+    ```
+
+33. 查询课程名称为「数学」，且分数低于 60 的学生姓名和分数
+    
+    ```mysql
+    select student_name,score from student right join score on student.student_id=score.student_id left join course on score.course_id=course.course_id where course_name='数学' and score<60;
+    ```
+
+34. 查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）
+    
+    ```mysql
+    select s2.student_name,s1.* from score s1 right join student s2 on s1.student_id=s2.student_id;
+    ```
+
+35. 查询任何一门课程成绩在 70 分以上的姓名、课程名称和分数
+    
+    ```mysql
+    select s1.student_name,c.course_name,s2.score from student s1 right join score s2 on s1.student_id=s2.student_id left join course c on s2.course_id=c.course_id where score>70;
+    ```
+
+36. 查询不及格的课程
+    
+    ```mysql
+    select distinct c.course_name from score s2 left join course c on s2.course_id=c.course_id where score<60;
+    ```
+
+37. 查询课程编号为 1 且课程成绩在 80 分以上的学生的学号和姓名
+    
+    ```mysql
+    select s1.student_id,s2.student_name from score s1,student s2 where course_id=1 and score>80 and s1.student_id=s2.student_id;
+    ```
+
+38. 求每门课程的学生人数
+    
+    ```mysql
+    select distinct course_id,count(student_id) over (partition by course_id) from score;
+    ```
+
+39. 成绩不重复，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩
+
+40. 成绩有重复的情况下，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩
+
+41. 查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩
+    
+    ```mysql
+    select distinct s1.* from score s1,score s2 where s1.score=s2.score and s1.course_id!=s2.course_id;
+    ```
+
+42. 查询每门功成绩最好的前两名
+    
+    ```mysql
+    select * from 
+    (select student_id,score,rank() over (partition by course_id order by score desc) ranks from score) s
+    where ranks<=2;
+    ```
+
+43. 统计每门课程的学生选修人数（超过 5 人的课程才统计）。
+    
+    ```mysql
+    select course_id,count(student_id) from score group by course_id having count(student_id)>5;
+    ```
+
+44. 检索至少选修两门课程的学生学号
+    
+    ```mysql
+    select student_id
+    from score
+    group by student_id
+    having count(course_id)>=2;
+    ```
+
+45. 查询选修了全部课程的学生信息
+    
+    ```mysql
+    select s2.* from score s1 right join student s2 on s1.student_id=s2.student_id group by student_id having count(course_id)>=(select count(course_id) from course);
+    ```
+
+46. 查询各学生的年龄，只按年份来算
+    
+    ```mysql
+    select student_name,year(now())-year(birthday) from student;
+    ```
+
+47. 按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一
+    
+    ```mysql
+    select birthday,(date_format(now(),'%y') - date_format(birthday,'%y') -
+                (case when date_format(now(),'%m%d') > date_format(birthday,'%m%d') then 0 else 1 end)) as age
+    from student;
+    ```
+
+48. 查询本周过生日的学生
+    
+    ```mysql
+    select * from student where day(birthday) between 16 and 22 and month(birthday)=month(now());
+    ```
+
+49. 查询下周过生日的学生
+    
+    ```mysql
+    select * from student where day(birthday) between 23 and 29 and month(birthday)=month(now());
+    ```
+
+50. 查询本月过生日的学生
+    
+    ```mysql
+    select * from student where month(birthday)=month(now());
+    ```
+
+51. 查询下月过生日的学生
+    
+    ```mysql
+    select * from student where month(birthday)=month(now())+1;
+    ```