SQL ReferenceSQL 函数HLL 函数HLL_EMPTY本页总览HLL_EMPTYHLL_EMPTYdescriptionSyntaxHLL_EMPTY(value)HLL_EMPTY 返回一个 hll 类型的空值。exampleMySQL > select hll_cardinality(hll_empty());+------------------------------+| hll_cardinality(hll_empty()) |+------------------------------+| 0 |+------------------------------+keywordsHLL,HLL_EMPTY