7a0c7f45b2
The english documents is translated by machine. So It may has some mistake. We will fix them later
482 B
482 B
'35; NDV Description '35;'35;' 35; 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.
'35;'35; example
MySQL > select ndv(query_id) from log_statis group by datetime;
+-----------------+
| ndv(`query_id`) |
+-----------------+
| 17721 |
+-----------------+
##keyword NDV