1.3 KiB
1.3 KiB
title, language
| title | language |
|---|---|
| NDV | en |
NDV
Description
Syntax
NDV (expr)
Returns an approximate aggregation function similar to the result of COUNT (DISTINCT col).
It combines COUNT and DISTINCT faster and uses fixed-size memory, so less memory can be used for columns with high cardinality.
example
MySQL > select ndv(query_id) from log_statis group by datetime;
+-----------------+
| ndv(`query_id`) |
+-----------------+
| 17721 |
+-----------------+
##keyword NDV