Hive数据仓库行转列

查了很多资料发现网上很多文章都是转发和抄袭，有些问题。这里分享一个自己项目中使用的行转列例子，供大家参考。代码如下：

SELECT
  my_id,
  nm_cd_map['A'] AS my_cd_a,
  nm_cd_map['B'] AS my_cd_b,
  nm_cd_map['C'] AS my_cd_c,
  nm_num_map['A'] AS my_num_a,
  nm_num_map['B'] AS my_num_b,
  nm_num_map['C'] AS my_num_c
FROM
  (
    SELECT
      t.my_id,
      STR_TO_MAP(my_nm_cds,';',':') AS nm_cd_map,
      STR_TO_MAP(my_nm_nums,';',':') AS nm_num_map
    FROM
      (
        SELECT
          my_id,
          CONCAT_WS(';',COLLECT_LIST(CONCAT(my_nm,':',my_cd))) AS my_nm_cds,
          CONCAT_WS(';',COLLECT_LIST(CONCAT(my_nm,':',my_num))) AS my_nm_nums
        FROM
          (
            SELECT '1' AS my_id,'A' AS my_nm,'D01' AS my_cd,19 AS my_num
            UNION ALL
            SELECT '1' AS my_id,'B' AS my_nm,'D04' AS my_cd,18 AS my_num
            UNION ALL
            SELECT服务器托管网 '1' AS my_id,'C' AS my_nm,'D02' AS my_cd,17 AS my_num
            UNION ALL
            SELECT '2' AS my_id,'A' AS my_nm,'D03' AS my_cd,16 AS my_num
            UNION ALL
            SELECT '2' AS my_id,'B' AS my_nm,'D05' AS my_cd,15 AS my_num
            UNION ALL
            SELECT '2' AS my_id,'C' AS my_nm,'D06' AS my_cd,14 AS my_num
          )
        GROUP BY my_id
      ) t
  ) t
WHERE 1=1;

如果是在SparkSQL或Presto平台，或者阿里云的MaxCompute平台，还可使用如下方式：

-- 其实也可使用CONCAT然后STR_TO_MAP的方式，或者用MAP_FROM_ARRAYS，再或者用数组排序后ARRAY[n] AS的方式
SELECT
  my_id,
  nm_cd_map['A'] AS my_cd_a,
  nm_cd_map['B'] AS my_cd_b,
  nm_cd_map['C'] AS my_cd_c,
  nm_num_map['A'] AS my_num_a,
  nm_num_map['B'] AS my_num_b,
  nm_num_map['C'] AS my_num_c
FROM
  (
    SELECT
      t.my_id,
      MAP_FROM_ENTRIES(COLLECT_LIST(nm_cd)) AS nm_cd_map,
      MAP_FROM_ENTRIES(COLLECT_LIST(nm_num)) AS nm_num_map
    FROM
      (
        SELECT
          my_id,
          my_nm,
          my_cd,
          my_num,
          STRUCT(my_nm,my_cd) AS nm_cd,
          STRUCT(my_nm,my_num) AS nm_num
        FROM
          (
            SELECT '1' AS my_id,'A' AS my_nm,'D01' AS my_cd,19 AS my_num
            UNION ALL
            SELECT '1' AS my_id,'B' AS my_nm,'D04' AS my_cd,18 AS my_num
            UNION ALL
            SELECT '1' AS my_id,'C' AS my_nm,'D02' AS my_cd,17 AS my_num
            UNION ALL
            SELECT '2' AS my_id,'A' AS my_nm,'D03' AS my_cd,16 AS my_num
            UNION ALL
            SELECT '2' AS my_id,'B' AS my_nm,'D05' AS my_cd,15 AS my_num
            UNION ALL
            SELECT '2' AS my_id,'C' AS my_nm,'D06' AS my_cd,14 AS my_num
          )
      ) t
    G服务器托管网ROUP BY my_id
  ) t
WHERE 1=1;

服务器托管，北京服务器托管，服务器租用 http://www.fwqtg.net

相关推荐: 「优选算法」：山脉数组的峰顶索引

一、题目 符合下列属性的数组arr称为山脉数组： arr.length >= 3 存在i（0 ）使得： arr[0] arr[i] > arr[i+1] > … > arr[arr.length – 1] 给你由整数组成的山脉数组a…