HLL_FROM_BASE64
更新时间：2025-10-16
描述
将一个 base64 编码的字符串（通常由 HLL_TO_BASE64 函数生成）转换为 HLL 类型。如果输入字符串不合法或为 NULL，则返回 NULL。
语法
SQL
1HLL_FROM_BASE64(<input>)参数
| 参数 | 说明 |
|---|---|
<input> |
base64 编码的字符串，通常由 HLL_TO_BASE64 函数生成。如果字符串不合法，则返回 NULL。 |
示例
SQL
1select hll_union_agg(hll_from_base64(hll_to_base64(pv))), hll_union_agg(pv) from test_hll;
Text
1+---------------------------------------------------+-------------------+
2| hll_union_agg(hll_from_base64(hll_to_base64(pv))) | hll_union_agg(pv) |
3+---------------------------------------------------+-------------------+
4| 3 | 3 |
5+---------------------------------------------------+-------------------+
SQL
1select hll_cardinality(hll_from_base64(hll_to_base64(hll_hash('abc'))));
Text
1+------------------------------------------------------------------+
2| hll_cardinality(hll_from_base64(hll_to_base64(hll_hash('abc')))) |
3+------------------------------------------------------------------+
4| 1 |
5+------------------------------------------------------------------+
SQL
1select hll_cardinality(hll_from_base64(hll_to_base64(hll_hash(''))));
Text
1+---------------------------------------------------------------+
2| hll_cardinality(hll_from_base64(hll_to_base64(hll_hash('')))) |
3+---------------------------------------------------------------+
4| 1 |
5+---------------------------------------------------------------+
SQL
1select hll_cardinality(hll_from_base64(hll_to_base64(hll_hash(NULL))));
Text
1+-----------------------------------------------------------------+
2| hll_cardinality(hll_from_base64(hll_to_base64(hll_hash(NULL)))) |
3+-----------------------------------------------------------------+
4| 0 |
5+-----------------------------------------------------------------+