一.SQL语言查询选修了全部课程的学生的学号和姓名. 两种解决途径: 第一种: 我们可以表示为在SC表中某个学生选修的课程数等于C表中课程总数.相应的SQL语言如下: select S#,SNAME from S where S# in (select S# from SC group by S# --根据Sno分组,统计每个学生选修了几门课程.如果等于C表课程的总数,就是我们要找的S# having count(*) = (select count(*) from C))--统计C表中共有几门
select sname from student where not exists (select * from course where not exists (select * from sc where sno =student.sno and cno=course.cno); 最内部的 select * from sc where sno=student.sno and cno = course.cno是查询出所有已经选择过课程的学生及相应课程,select * from cour
3.1.g 找出在2009年秋季拥有最多选课人数的课程 3.1 使用大学模式,用SQL写出如下查询. g) 找出在2009年秋季拥有最多选课人数的课程段. 注:本题来自于 数据库系统概念 第六版 机械工程出版社 第三章习题 解:满足题意得查询代码如下: WITH R AS ( SELECT Course_id, Sec_id, COUNT (Id) AS Cnt_id FROM Takes NATURAL JOIN Section WHERE Year = 2009 AND Semester =
前几天求职面试,有一道SQL题:给出三个表:学生.课程.成绩,求选修了所有课程的学生. 一道看似很简单的问题,把我难住了,我改了又改,涂涂画画,抓耳挠腮,因为试卷没有多少空白位置了,最后只好放弃.心情大受影响,尽管最后还是获得offer. 但是心中有愧呀! 于是在机器上试了试: 先建好表 use test; go create table student(sno varchar(50) not null,name varchar(50) not null); insert into studen
有些时候,有些作业遇到问题执行时间过长,因此我写了一个脚本可以根据历史记录,找出执行时间过长的作业,在监控中就可以及时发现这些作业并尽早解决,代码如下: SELECT sj.name , sja.start_execution_date,DATEDIFF (SECOND ,sja.start_execution_date,GETDATE() ) AS ExecutedMin,ja.AvgRuntimeOnSucceed FROM msdb.dbo.sysjobactivity AS
Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all the elements of [1, n] inclusive that do not appear in this array. Could you do it without extra space and in O(n) runtime?
Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all the elements that appear twice in this array. Could you do it without extra space and in O(n) runtime? Example: Input: [4,3,2,7,
Median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value. So the median is the mean of the two middle value. Examples: [2,3,4] , the median is 3 [2,3], the median is (2 + 3) / 2 = 2.5 Design a d
在一个SQL Server表中一行的多个列找出最大值 有时候我们需要从多个相同的列里(这些列的数据类型相同)找出最大的那个值,并显示 这里给出一个例子 IF (OBJECT_ID('tempdb..##TestTable') IS NOT NULL) DROP TABLE ##TestTable CREATE TABLE ##TestTable ( ID ,) PRIMARY KEY, Name ), UpdateByApp1Date DATETIME, UpdateByApp2Date DAT
就是找x+y=-z的组合 转化为找出值为-z满足x+y=-z的组合 解法一: 为了查找,首先想到排序,为了后面的二分,nlogn, 然后x+y的组合得n^2的复杂度,加上查找是否为-z,复杂度为nlogn + n^2 * logn 解法二: 还是先从小到大排序 nlogn 假设数组排序后为 a b c d e f 我们还是要找x+y=-z 会发现-z存在的可能只能是a+f和b+e,不会存在a+e和b+f这种情况(这里很重要,保证了算法的正确性),所以两个指针一头一尾往中间扫,肯定能找出来 fis
问题: Given an array of integers, every element appears three times except for one. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? Single Number I 升级版,一个数组中其它数出现了
/** * 找出未出现的最小正整数 * @param A * @param n * @date 2016-10-7 * @author shaobn */ public static int findArrayMex(int[] a,int n){ int count = n; int temp = 0; int dir = 1; int num = 0; for(int i = 0;i<count-1;i++){ if(a[i]>a[i+1]){ temp = a[i]; a[i]= a[i