HiveQL函数3—集合、类型转换函数
作者：互联网
目录
集合函数
HiveQL支持的集合函数如下
| 函数名 | 返回类型 | 描述 |
|---|---|---|
| size(Map<K.V>) | int | 计算map的元素个数 |
| size(Array) | int | 计算数组的元素个数 |
| map_keys(Map<K.V>) | array | 返回map中的所有key |
| map_values(Map<K.V>) | array | 返回map中的所有value |
| array_contains(Array, value) | boolean | 如该数组Array包含value返回true，否则返回false |
| sort_array(Array) | array | 按自然顺序对数组从低到高进行排序并返回 |
示例1
--size(Map<K,V>) ，size(Array\<T\>)
> SELECT
SIZE(work_place) as array_size,
SIZE(skills_score) as map_size,
SIZE(depart_title) as complex_size,
SIZE(depart_title["Product"]) as nest_size
FROM employee_internal;
+-------------+-----------+---------------+------------+
| array_size | map_size | complex_size | nest_size |
+-------------+-----------+---------------+------------+
| 2 | 1 | 1 | 1 |
| 1 | 1 | 2 | 1 |
| 1 | 1 | 2 | -1 |
| 1 | 2 | 1 | -1 |
+-------------+-----------+---------------+------------+
> SELECT size(null), size(array(null)), size(array());
+------+------+------+
| _c0 | _c1 | _c2 |
+------+------+------+
| -1 | 1 | 0 |
+------+------+------+
示例2
--array_contains(Array<T>, value)，sort_array(Array<T>)
>SELECT
array_contains(work_place, 'Toronto') as is_Toronto,
sort_array(work_place) as sorted_array
FROM employee_internal;
+-------------+-------------------------+
| is_toronto | sorted_array |
+-------------+-------------------------+
| true | ["Montreal","Toronto"] |
| false | ["Montreal"] |
| false | ["New York"] |
| false | ["Vancouver"] |
+-------------+-------------------------+
类型转换函数
1. binary(string|binary)
返回值：binary
功能：将输入的值转换成二进制
示例：
> select binary('hello') as f1;
+--------+
| f1 |
+--------+
| hello |
+--------+
2. cast(expr as <type>)
返回值：指定类型
功能：将expr转换成type类型 如：cast(“1” as BIGINT) 将字符串1转换成了BIGINT类型，如果转换失败将返回NULL。对于cast(expr as boolean)，如果字符串不为空则会返回true。
示例：
> select cast('123' as BIGINT) as f1;
+------+
| f1 |
+------+
| 123 |
+------+
> select cast('123' as boolean) as f1;
+-------+
| f1 |
+-------+
| true |
+-------+
参考
https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF#LanguageManualUDF-CollectionFunctions
https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF#LanguageManualUDF-TypeConversionFunctions
书籍 Apache Hive Essentials Second Edition (by Dayong Du) Chapter 5
看得出的就是
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标签：类型转换,map,函数,HiveQL,示例,cast,array,Array,size 来源： https://blog.csdn.net/CPP_MAYIBO/article/details/104065151