COUNT
description
Syntax
COUNT([DISTINCT] expr)
用于返回满足要求的行的数目
example
MySQL > select count(*) from log_statis group by datetime;
+----------+
| count(*) |
+----------+
| 28515903 |
+----------+
MySQL > select count(datetime) from log_statis group by datetime;
+-------------------+
| count(`datetime`) |
+-------------------+
| 28521682 |
+-------------------+
MySQL > select count(distinct datetime) from log_statis group by datetime;
+-------------------------------+
| count(DISTINCT `datetime`) |
+-------------------------------+
| 71045 |
+-------------------------------+keywords
COUNT