1d9b3aeee7
The error format '##keyword' in a lot of docs. This pr is to repair document format. #4335
1.4 KiB
1.4 KiB
title, language
| title | language |
|---|---|
| APPROX_COUNT_DISTINCT | zh-CN |
APPROX_COUNT_DISTINCT
description
Syntax
APPROX_COUNT_DISTINCT(expr)
返回类似于 COUNT(DISTINCT col) 结果的近似值聚合函数。
它比 COUNT 和 DISTINCT 组合的速度更快，并使用固定大小的内存，因此对于高基数的列可以使用更少的内存。
example
MySQL > select approx_count_distinct(query_id) from log_statis group by datetime;
+-----------------+
| approx_count_distinct(`query_id`) |
+-----------------+
| 17721 |
+-----------------+
keyword
APPROX_COUNT_DISTINCT