mysql 分组函数

#分组函数:用作统计使用,可嵌套使用USE myemployees;#sum 求和SELECT SUM(salary) FROM employees;#avg 求平均SELECT AVG(salary) FROM employees;#max 求最大值SELECT MAX(salary) FROM employees;#min 求最小值SELECT MIN(salary) FROM employees;#count 计算个数SELECT COUNT(salary) FROM employees;