Hive练习题之行转列(二)

需求:

+-------------+---------------+-----------------+----------------+---------------------+------------------+
| student.id  | student.name  | student.gender  | student.birth  | student.department  | student.address  |
+-------------+---------------+-----------------+----------------+---------------------+------------------+
| 201901      | 张大佬           | 男               | 1985           | 计算机系                | 北京市海淀区           |
| 201902      | 郭大侠           | 男               | 1986           | 中文系                 | 北京市昌平区           |
| 201903      | 张三            | 女               | 1990           | 中文系                 | 湖南省永州市           |
| 201904      | 李四            | 男               | 1990           | 英语系                 | 辽宁市阜新市           |
| 201905      | 王五            | 女               | 1991           | 英语系                 | 福建省厦门市           |
| 201906      | 王六            | 男               | 1988           | 计算机系                | 湖南省衡阳市           |
+-------------+---------------+-----------------+----------------+---------------------+------------------+

请写一条sql将以上数据, 转换成下面的结果

+-------+----+----+-----+
|  院系    | 男  | 女  | 总计  |
+-------+----+----+-----+
| 中文系    | 1  | 1  | 2   |
| 英语系    | 1  | 1  | 2   |
| 计算机系  | 2  | 0  | 2   |
+-------+----+----+-----+

– 建表

create table if not exists test.student (
      id string,
      name string,
      gender string,
      birth string,
      department string,
      address string
)
row format delimited fields terminated by ",";

–导入数据

vi /doit/student
201901,张大佬,男,1985,计算机系,北京市海淀区
201902,郭大侠,男,1986,中文系,北京市昌平区
201903,张三,女,1990,中文系,湖南省永州市
201904,李四,男,1990,英语系,辽宁市阜新市
201905,王五,女,1991,英语系,福建省厦门市
201906,王六,男,1988,计算机系,湖南省衡阳市

load data local inpath "/doit/student" into table test.student;

– 方法1

select 
      `院系`,
      sum(`男`) `男`,
      sum(`女`) `女`,
      sum(`男`) + sum(`女`) as `总计`
from
(
    select department `院系`,
    case gender when "男" then 1 else 0 end `男`,
    case gender when "女" then 1 else 0 end `女`
    from student
) a
group by `院系`;

– 方法1加强

select
     department  `院系`,
     sum(case gender when "男" then 1 else 0 end) `男`, 
     sum(case gender when "女" then 1 else 0 end) `女`,
     sum(case  when gender = "女" or  gender = "男" then 1 else 0 end) `总计`
from
    student
group by department

– 方法2

with tmp as (
select
     department,
     gender,
     count (1) cnt
from student
group by department,gender)

select
     department `院系`,
     nvl(gc['男'],0) `男`,
     nvl(gc['女'],0) `女`,
	 -- floor是向下取整
     floor(nvl(gc['男'],0) + nvl(gc['女'],0)) `总计`
from
(
        select
             department,
             str_to_map(concat_ws(",",collect_list(concat_ws(":",gender,cast (cnt as string)))),",",":") gc
        from
       		    tmp
        group by 
		        department
) t