SQL serve聚合函数与分组查询
–聚合函数包括
![SQL serve聚合函数与分组查询 SQL serve聚合函数与分组查询](/default/index/img?u=aHR0cHM6Ly9waWFuc2hlbi5jb20vaW1hZ2VzLzExLzg5NDMwNTAyOGVhMzViYTE1MWMzOTc2Mjg3YjE0NTkzLnBuZw==)
例1:统计课程编号为CO1的最高分、最低分、平均分、学生数量
select MAX(grade) as ‘最高分’, MIN(grade) as ‘最低分’,
AVG(grade) as ’ 平均分’,COUNT(*) as ‘学生数量’,
from t_score
where cno =‘CO1’
例2:统计每一门课程的最高分、最低分、平均分、学生数量
select MAX(grade) as ‘最高分’, MIN(grade) as ‘最低分’,
AVG(grade) as ’ 平均分’,COUNT(*) as ‘学生数量’,
from t_score
GROUP BY cno
例3
聚合函数:
最大值max,最小值min,平均值avg,求和sum,总数count。
分组group by
分组条件:group by having…