SQL语句数据行操作补充
            create table tb12(
                id int auto_increment primary key,
                name varchar(32),
                age int
            )engine=innodb default charset=utf8;
    
        增
            insert into tb11(name,age) values('alex',12);
            
            insert into tb11(name,age) values('alex',12),('root',18);
            
            insert into tb12(name,age) select name,age from tb11;
        删
            delete from tb12;
            delete from tb12 where id !=2 
            delete from tb12 where id =2 
            delete from tb12 where id > 2 
            delete from tb12 where id >=2 
            delete from tb12 where id >=2 or name='alex'
        
        改
            update tb12 set name='alex' where id>12 and name='xx'
            update tb12 set name='alex',age=19 where id>12 and name='xx'
        查
            
            select * from tb12;
            
            select id,name from tb12;
            
            select id,name from tb12 where id > 10 or name ='xxx';
            
            select id,name as cname from tb12 where id > 10 or name ='xxx';
            
            select name,age,11 from tb12;
            
            其他：
                select * from tb12 where id != 1
                select * from tb12 where id in (1,5,12);
                select * from tb12 where id not in (1,5,12);
                select * from tb12 where id in (select id from tb11)
                select * from tb12 where id between 5 and 12;
    
            
                通配符：
                
                select * from tb12 where name like "a%"
                select * from tb12 where name like "a_"
    
            
                分页：
                
                    select * from tb12 limit 10;
                    
                    select * from tb12 limit 0,10;
                    select * from tb12 limit 10,10;
                    select * from tb12 limit 20,10;
                    
                    select * from tb12 limit 10 offset 20;
        
        
                    # page = input('请输入要查看的页码')
                    # page = int(page)
                    # (page-1) * 10
                    # select * from tb12 limit 0,10; 1 
                    # select * from tb12 limit 10,10;2
                
                
                排序：
                    select * from tb12 order by id desc; 大到小
                    select * from tb12 order by id asc;  小到大
                     select * from tb12 order by age desc,id desc;
                     
                    取后10条数据
                    select * from tb12 order by id desc limit 10;
            
                分组：
                
                    select count(id),max(id),part_id from userinfo5 group by part_id;
                    
                    count
                    max
                    min
                    sum
                    avg
                    
                    **** 如果对于聚合函数结果进行二次筛选时？必须使用having ****
                    select count(id),part_id from userinfo5 group by part_id having count(id) > 1;
                    
                    select count(id),part_id from userinfo5 where id > 0 group by part_id having count(id) > 1;
            
                    
                连表操作：
                
                    select * from userinfo5,department5
                    
                    select * from userinfo5,department5 where userinfo5.part_id = department5.id
                    

                    select * from userinfo5 left join department5 on userinfo5.part_id = department5.id
                    select * from department5 left join userinfo5 on userinfo5.part_id = department5.id
                    # userinfo5左边全部显示
                    
                    
                    # select * from userinfo5 right join department5 on userinfo5.part_id = department5.id
                    # department5右边全部显示
                
                
                
                    select * from userinfo5 innder join department5 on userinfo5.part_id = department5.id
                    将出现null时一行隐藏
                    
                    
                
                
                
                
                    select * from 
                        department5 
                    left join userinfo5 on userinfo5.part_id = department5.id
                    left join userinfo6 on userinfo5.part_id = department5.id
                
                
                    select 
                        score.sid,
                        student.sid 
                        from 
                    score

                        left join student on score.student_id = student.sid

                        left join course on score.course_id = course.cid

                        left join class on student.class_id = class.cid

                        left join teacher on course.teacher_id=teacher.tid
                    
            
            
            
            select count(id) from userinfo5;
                

            create table tb12(
                id int auto_increment primary key,
                name varchar(32),
                age int
            )engine=innodb default charset=utf8;

insert into tb11(name,age) values('alex',12);

insert into tb11(name,age) values('alex',12);

insert into tb12(name,age) select name,age from tb11;