ARRAY_APPROX_COUNT_DISTINCT

返回数组中不同元素数量的近似值（忽略 NULL）。实现基于与 APPROX_COUNT_DISTINCT 相同的 HyperLogLog 算法。

语法

ARRAY_APPROX_COUNT_DISTINCT(<array>)

返回类型

BIGINT

示例

SELECT ARRAY_APPROX_COUNT_DISTINCT([1, 1, 2, 3, 3, 3]) AS approx_cnt;

+------------+
| approx_cnt |
+------------+
|          3 |
+------------+

SELECT ARRAY_APPROX_COUNT_DISTINCT([NULL, 'a', 'a', 'b']) AS approx_cnt_text;

+------------------+
| approx_cnt_text  |
+------------------+
|                2 |
+------------------+