将Impala sql转置/将1行旋转为列或按范围分组的替代方法

Question

SELECT 
    SUM(CASE WHEN age >= 80 THEN 1 ELSE 0 END) AS '>=80',
    SUM(CASE WHEN age BETWEEN 70 AND 79 THEN 1 ELSE 0 END) AS '70-79',
    SUM(CASE WHEN age BETWEEN 60 AND 69 THEN 1 ELSE 0 END) AS '60-69',
    SUM(CASE WHEN age BETWEEN 50 AND 59 THEN 1 ELSE 0 END) AS '50-59',
    SUM(CASE WHEN age BETWEEN 40 AND 49 THEN 1 ELSE 0 END) AS '40-49',
    SUM(CASE WHEN age BETWEEN 30 AND 39 THEN 1 ELSE 0 END) AS '30-39',
    SUM(CASE WHEN age BETWEEN 20 AND 30 THEN 1 ELSE 0 END) AS '20-29',
    SUM(CASE WHEN age BETWEEN 10 AND 19 THEN 1 ELSE 0 END) AS '10-19',
    SUM(CASE WHEN age BETWEEN 0 AND 9 THEN 1 ELSE 0 END) AS '0-9'
FROM (SELECT * FROM table) a

我正在使用上面的查询来存储年龄范围，并且输出：

+------+-------+-------+-------+-------+-------+--------+---------+---------+
| >=80 | 70-79 | 60-69 | 50-59 | 40-49 | 30-39 | 20-29  | 10-19   | 0-9     |
+------+-------+-------+-------+-------+-------+--------+---------+---------+
| 136  | 394   | 1273  | 2530  | 3298  | 15384 | 194099 | 2244405 | 9780789 |
+------+-------+-------+-------+-------+-------+--------+---------+---------+

我需要将其转换为列格式，或者找到一种替代的存储方法，以允许上述查询生成与值行相反的列。

期望的输出：

+-----------+----------*
| age_range | freq     | 
+-----------+----------*
| >=80      | 136      |
+-----------+----------*
| 70-79     | 394      |
+-----------+----------*
| 60-69     | 1273     |
+-----------+----------*
| 50-59     | 2530     |
+-----------+----------*
| 40-49     | 3298     |
+-----------+----------*
| 30-39     | 15384    |
+-----------+----------*
| 20-29     | 194099   |
+-----------+----------*
| 10-19     | 2244405  |
+-----------+----------*
| 0-9       | 9780789  |
+-----------+----------*

据我所知，Impala不支持数据透视？

感谢您的帮助，谢谢

Answer 1

case键使用group by表达式：

SELECT (CASE WHEN age >= 80 THEN '>=80',
             WHEN age BETWEEN 70 AND 79 THEN '70-79',
             WHEN age BETWEEN 60 AND 69 THEN '60-69',
             WHEN age BETWEEN 50 AND 59 THEN '50-59',
             WHEN age BETWEEN 40 AND 49 THEN '40-49',
             WHEN age BETWEEN 30 AND 39 THEN '30-39',
             WHEN age BETWEEN 20 AND 30 THEN '20-29',
             WHEN age BETWEEN 10 AND 19 THEN'10-19',
             WHEN age BETWEEN 0 AND 9 THEN '0-9'
        END) as age_group,
      COUNT(*)
FROM a
GROUP BY age_group;