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竖表转横表竖表结构:NameCourseGrade张三语文75张三数学80张三英语90李四语文95李四数学55转换后横表结构:Name语文数学英语张三758090李四95550SQL语句:1 select Name,2 sum(case Course when '语文' then Grade els... 阅读全文
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int a = 2,b = 3;public void ChangeNum(){ a = a ^ b; b = a ^ b; //a ^ b ^ b = a,b ^ a ^ a = b a = a ^ b;} 阅读全文
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简单的单例: 1 public class Student 2 { 3 //1。私有静态变量 4 private static Student stu = null; 5 6 //2。私有化构造函数 7 private Stu... 阅读全文