01由不等概率转变为等概率：

package Random.随机函数;

/**
 * 不等概率的01----->等概率01
 */
public class Test2 {

    public  static  int x(){
        return Math.random() < 0.84? 0 : 1;
    }

    /**
     * 等概率的01   先判断一次，ans要是是0，在判断一次，要是还是0，返回0，要是1就重来一次，同理1也这样，01就是等概率
     * @return
     */
    public  static  int y(){
        int ans = 0;
        do {
            ans = x();
        }while (ans==x());
            return  ans;
    }


}

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MYSQL

这个题是三个表，我们的思维就是化成两个表，将其中两个表通过内连接合并，然后再和第一个表左连接查询

SELECT e.last_name, e.first_name, b.dept_name
FROM employees AS e
LEFT JOIN (SELECT d.dept_no,d.dept_name,de.emp_no
FROM departments AS d
INNER JOIN dept_emp AS de
ON d.dept_no=de.dept_no
) AS b
ON e.emp_no=b.emp_no;