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  • 模糊查询

    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

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  • 原文地址:https://www.cnblogs.com/lowerma/p/10136992.html
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