由一条sql语句引发的学习之二

select m.*,case
when  m.max_num > n.maxvalue then '被考核' else '正常' end as maxvalue , 
nvl(n.CATEGORY,'其他') from (
select 'didi' x1 ,a.templateid ,b.template_name ,sum(a.num) send_num,count(1) user_num,max(a.num) max_num,trunc(sum(a.num)/count(1)) seg_num
from (
select phone_no, templateid, count(1)num
  from math_score
 where send_time > trunc(sysdate)
 group by  phone_no,  templateid
having count(1) > $anum) a, school_info b
where a.templateid =  b.template_id  ${tiaojian}
group by a.templateid,b.template_name
union all
select 'didi',a.templateid,b.template_name  ,sum(a.num) send_num,count(1) user_num,max(a.num) max_num,trunc(sum(a.num)/count(1)) seg_num
from (
select phone_no, templateid, count(1)num
  from english_score
 where send_time > trunc(sysdate) 
 group by  phone_no,  templateid
having count(1) > $anum) a, school_info b
where a.templateid =  b.template_id  ${tiaojian}
group by a.templateid,b.template_name
union all
select 'didi',a.templateid,b.template_name  ,sum(a.num) send_num,count(1) user_num,max(a.num) max_num,trunc(sum(a.num)/count(1)) seg_num
from (
select phone_no, templateid, count(1)num
  from chinese_score
 where send_time > trunc(sysdate)
 group by  phone_no,  templateid
having count(1) > $anum) a, school_info b
where a.templateid =  b.template_id  ${tiaojian}
group by a.templateid,b.template_name)  m ,school_info n
where m.templateid = n.template_id 
order by user_num desc;

  场景：

  求取一个学校内，每个(语文\数学\英语)老师所带学生的班级名、班级总分、班级人数、最高分，平均分、及格率，及格率是否符合正常情况(考核老师）

  school_info表字段：老师id、班级、班级人数、及格率...

  math_score表字段：老师id、班级、手机号、学生信息、数学成绩...

  关键语法解析：

  1、NVL函数：从两个表达式返回一个非 null 值。

  2、case用法：详细解析

  3、from+表名跟from+select语句作用一样。

  4、Union和Union All区别：详解

       Union：对两个结果集进行并集操作，不包括重复行，同时进行默认规则的排序；

       Union All：对两个结果集进行并集操作，包括重复行，不进行排序；

 

 

标签：语句,count,sql,之二,num,template,templateid,where,select
来源： https://blog.csdn.net/m0_37806112/article/details/101096978