ARRAY_AVG
array_avg
描述
计算数组中所有数值元素的平均值。函数会跳过数组中的 null 值和非数值元素,只对有效的数值元素进行平均值计算。
语法
array_avg(ARRAY<T> arr)
参数
arr
:ARRAY类型,要计算平均值的数组。支持列名或常量值。
T 支持的类型:
- 数值类型:TINYINT、SMALLINT、INT、BIGINT、LARGEINT、FLOAT、DOUBLE、DECIMAL
返回值
返回类型:根据输入类型自动选择
返回值含义:
- 返回数组中所有有效数值元素的平均值
- NULL:或数组为空,或所有元素都为 NULL 或无法转换为数值
使用说明:
- 空数组返回 NULL,只有一个元素的数组返回该元素的值
- 嵌套数组、MAP、STRUCT 等复杂类型不支持平均值计算,调用会报错
- 对数组元素中的 null 值:null 元素不参与平均值计算
示例
CREATE TABLE array_avg_test (
id INT,
int_array ARRAY<INT>,
double_array ARRAY<DOUBLE>,
mixed_array ARRAY<STRING>
)
DUPLICATE KEY(id)
DISTRIBUTED BY HASH(id) BUCKETS 3
PROPERTIES (
"replication_num" = "1"
);
INSERT INTO array_avg_test VALUES
(1, [1, 2, 3, 4, 5], [1.1, 2.2, 3.3, 4.4, 5.5], ['1', '2', '3', '4', '5']),
(2, [10, 20, 30], [10.5, 20.5, 30.5], ['10', '20', '30']),
(3, [], [], []),
(4, NULL, NULL, NULL),
(5, [1, null, 3, null, 5], [1.1, null, 3.3, null, 5.5], ['1', null, '3', null, '5']);
查询示例:
计算 double_array 的平均值:
SELECT array_avg(double_array) FROM array_avg_test WHERE id = 1;
+-------------------------+
| array_avg(double_array) |
+-------------------------+
| 3.3 |
+-------------------------+
计算混合类型数组的平均值,字符串会被转换为数值:
SELECT array_avg(mixed_array) FROM array_avg_test WHERE id = 1;
+------------------------+
| array_avg(mixed_array) |
+------------------------+
| 3 |
+------------------------+
空数组返回 NULL:
SELECT array_avg([]);
+----------------------+
| array_avg(int_array) |
+----------------------+
| NULL |
+----------------------+
NULL 数组返回 NULL:
SELECT array_avg(NULL);
+-----------------+
| array_avg(NULL) |
+-----------------+
| NULL |
+-----------------+
包含 null 的数组,null 元素不参与计算:
SELECT array_avg(int_array) FROM array_avg_test WHERE id = 5;
+----------------------+
| array_avg(int_array) |
+----------------------+
| 3 |
+----------------------+
复杂类型示例:
嵌套数组类型不支持,报错:
SELECT array_avg([[1,2,3]]);
ERROR 1105 (HY000): errCode = 2, detailMessage = array_avg([[1, 2, 3]]) does not support type: ARRAY<TINYINT>
map 类型不支持,报错:
SELECT array_avg([{'k':1},{'k':2}]);
ERROR 1105 (HY000): errCode = 2, detailMessage = array_avg([map('k', 1), map('k', 2)]) does not support type: MAP<VARCHAR(1),TINYINT>
参数数量错误会报错:
SELECT array_avg([1,2,3], [4,5,6]);
ERROR 1105 (HY000): errCode = 2, detailMessage = Can not found function 'array_avg' which has 2 arity. Candidate functions are: [array_avg(Expression)]
传入非数组类型时会报错:
SELECT array_avg('not_an_array');
ERROR 1105 (HY000): errCode = 2, detailMessage = Can not find the compatibility function signature: array_avg(VARCHAR(12))
Keywords
ARRAY, AVG, ARRAY_AVG