写代码对人的影响

一、每个学科的成绩第一名是谁？

0 问题描述

 基于学生成绩表输出每个科目的第一名是谁呢？

1 数据准备

with t1 as
         (
          select
               'zs'                                           as name,
               '[{"Chinese":80},{"Math":70},{"English":60}]' as score_ext
           union all
           select
               'ls'                                           as name,
               '[{"Chinese":90},{"Math":70},{"English":90}]' as score_ext
           union all
           select
               'ww'                                           as name,
               '[{"Chinese":60},{"Math":90},{"English":80}]' as score_ext
         ),
     t2 as
         (
          select
              name,
              -- 需要把 [] 和 " 和 {} 都给去掉，方面后面操作
              regexp_replace(score_ext, '\\[|\\{|\\}|\\"|\\]', '') as scores
          from t1
         ),
     t3 as (
         select
             name,
             split(score, ":")[0] as course,
             split(score, ":")[1] as score
         from t2
                  lateral view explode(split(scores, ',')) expl as score
     )

select
    name,
    course,
    score
from (
      select
          course,
          name,
          score,
          row_number() over (partition by course order by score desc) as rn
      from t3
     ) t4
where rn = 1;

2 数据分析

步骤1：采用 regexp_replace(score_ext, '\\[|\\{|\\}|\\"|\\]', '') as scores，去除相关符号后，t2输出：

步骤2：基于t2表进行lateral view explode 侧写炸裂时，t3输出：

步骤3：基于t3表进行 row_number() over (partition by course order by score desc) as rn
开窗排序（分组topN），t4输出：

3 小结

该题目利用（行转列）炸裂+开窗进行 解决；用到的Hive正则表达式如下：

(06)Hive——正则表达式_hive 正则表达式-CSDN博客