COUNT

Description

Syntax

COUNT([DISTINCT] expr)

Number of rows used to return the required rows

example

MySQL > select count(*) from log_statis group by datetime;
+----------+
| count(*) |
+----------+
| 28515903 |
+----------+
MySQL > select count(datetime) from log_statis group by datetime;
+-------------------+
count (`datetime') 1244;
+-------------------+
|         28521682  |
+-------------------+
MySQL > select count(distinct datetime) from log_statis group by datetime;
+-------------------------------+
| count(DISTINCT `datetime`)    |
+-------------------------------+
|                       71045   |
+-------------------------------+

keyword COUNT