第十二章查询代码

梦丶乾

于 2016-11-23 13:39:31 发布

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CC 4.0 BY-SA版权

本文链接：https://blog.youkuaiyun.com/qq_36074092/article/details/53304184

本文主要介绍了使用SQL进行数据查询的各种技巧，包括条件筛选、聚合计算、排序等操作，并展示了如何更新特定的数据记录。

select stuNo, stuName, stuSex, stuAge, stuSeat, stuAddress
from stulnfo where stuSex='男'

select stuNo, writtenExam
from stuMarks where writtenExam>=75 and writtenExam<=100

select AVG(writtenExam) as '笔试平均分',AVG(labExam) as '机试平均分'
from stuMarks where writtenExam<>0 and labExam<>0

select COUNT(*) as '学生总人数' from stuMarks

select COUNT(*) as '没有通过考试的人数' 
from stuMarks where writtenExam between 0 and 60 or labExam between 0 and 60

select stuNo, writtenExam, labExam,(writtenExam+labExam)/2 as '平均分'
from stuMarks

select stuNo,labExam,(writtenExam+labExam)/2 as '平均分'from stuMarks
order by (writtenExam+labExam)/2 desc



update stuMarks set writtenExam=100 where writtenExam>=95
update stuMarks set writtenExam+=5 where writtenExam<9