模糊查询和聚合函数

Posted 2021-01-28 mayuan01

SELECT * FROM Student UPDATE Student SET StudentName=‘王波‘ WHERE StudentNo=‘Y21003011‘

--模糊查询：查询学生表中姓’冯‘的学生记录 -- --‘%‘:匹配0-n个任意字符  --‘_‘匹配单个字符  --‘[]‘匹配区间内的值：如[13] --‘[^]‘匹配区间内不包含的值 SELECT * FROM Student WHERE StudentName LIKE ‘王_‘ SELECT * FROM Result WHERE SubjectId LIKE ‘[1-9]‘ SELECT * FROM Result WHERE SubjectId LIKE ‘[^1-3]‘ --查询空的数据行 SELECT * FROM Student WHERE Email=‘‘

--查询区间内数据:BETWEEN AND SELECT * FROM Result WHERE SubjectId BETWEEN 1 AND 10

--查询与列所匹配值相同的数据：IN SELECT * FROM Student WHERE Address IN (‘新疆乌鲁木齐‘,‘北京市海淀区五道口北大青鸟IT职业技术学院‘,‘黑龙江哈尔滨‘)

--聚合函数 --1.求和：SUM() SELECT SUM(StudentResult) AS ‘总成绩‘,Result.SubjectId FROM Result WHERE SubjectId=3

--2.平均值 SELECT AVG(StudentResult) AS ‘平均成绩‘ FROM Result

--3.最大值，最小值 SELECT MAX(StudentResult) AS ‘最高成绩‘ FROM Result SELECT MIN(StudentResult) AS ‘最低成绩‘ FROM Result

--4.统计记录数:COUNT(*)和COUNT(1)的区别 SELECT COUNT(StudentNo) AS ‘记录数‘ FROM Result