数据库聚合函数
聚合函数 sum ,avg,max,min,count
1总分
SELECT SUM(student_result) FROM result;
SELECT student_no,SUM(studet_result) FROM
result WHERE student_no62平均分 avg
SELECT AVG(studet_result) FROM result;3最大值 max 最小值 min
SELECT MAX(studet_r…
be located in / situated 坐落于/位于with an average altitude of 100 meters海拔covers an area of 2.3 millions square kilometers面积with a total area of about 5000 square kilometers面积be covered by覆盖a thickness of 50-80 meters厚度one of the birthplace of发…
在开发中遇到需要进行数据去重的查询,或删除重复数据的情况,整理如下:
1. distinct关键字
selectdistinct user_id, create_date
from order_info;2. 分组
selectuser_id,create_date
from order_info
group by user_id, create_date;3. 窗…