在Hive/SQL中获取具有最大值的行？

Question

我是Hive/SQL的新手,我遇到了一个相当简单的问题.我的数据如下:

+------------+--------------------+-----------------------+
| carrier_iD |     meandelay      |     meancanceled      |
+------------+--------------------+-----------------------+
| EV         | 13.795802119653473 | 0.028584251044292006  |
| VX         | 0.450591016548463  | 2.364066193853424E-4  |
| F9         | 10.898001378359766 | 0.00206753962784287   |
| AS         | 0.5071547420965062 | 0.0057404326123128135 |
| HA         | 1.2031093279839498 | 5.015045135406214E-4  |
| 9E         | 8.147899230704216  | 0.03876067292247866   |
| B6         | 9.45383857757506   | 0.003162096314343487  |
| UA         | 8.101511665305816  | 0.005467725574605967  |
| FL         | 0.7265068895709532 | 0.0041141513746490044 |
| WN         | 7.156119279121648  | 0.0057419058192869415 |
| DL         | 4.206288692245839  | 0.005123990066804269  |
| YV         | 6.316802855264404  | 0.029304029304029346  |
| US         | 3.2221527095063736 | 0.007984031936127766  |
| OO         | 6.954715814690328  | 0.02596499362466706   |
| MQ         | 9.74568222216328   | 0.025628100708354324  |
| AA         | 8.720522654298968  | 0.019242775597574157  |
+------------+--------------------+-----------------------+

我希望Hive返回具有meanDelay max值的行.我有:

SELECT CAST(MAX(meandelay) as FLOAT) FROM flightinfo;

确实返回最大值(我使用强制转换,因为我的值保存为STRING).那么:

SELECT * FROM flightinfo WHERE meandelay = (SELECT CAST(MAX(meandelay) AS FLOAT) FROM flightinfo);

我收到以下错误:

FAILED: ParseException line 1:44 cannot recognize input near 'select' 'cast' '(' in expression specification

Answer 1

使用窗口和分析功能

SELECT carrier_id, meandelay, meancanceled
FROM
 (SELECT carrier_id, meandelay, meancanceled,
         rank() over (order by cast(meandelay as float) desc) as r 
  FROM table) S 
WHERE S.r = 1;

如果多行具有相同的最大值,这也将解决问题,您将得到所有行作为结果.如果你只是想要一个行更改rank()到row_number()或添加其他期限的order by.

Answer 2

我不认为你的子查询是允许的......

快速浏览一下这里：

https://cwiki.apache.org/confluence/display/Hive/LanguageManual+SubQueries

状态：

从 Hive 0.13 开始，WHERE 子句支持某些类型的子查询。在这些查询中，查询结果可以被视为 IN 和 NOT IN 语句的常量（称为不相关子查询，因为子查询不引用父查询中的列）：