界面外观
先附上数据库中某一张表的数据
开始运行
先根据学生信息，抽象出相应的对象
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Model
{
public class StudentInfo
{
public string Sno { get; set; }
public string Sname { get; set; }
2022-05-25 18:11:41
411KB
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黑笔是我写的，红笔是我在网上找的答案。我俩参考表设置的不一样,我设置反了！
他这个语句好像也不是标准SQL，应该是MYSQL还是Oracle吧。希望老师解答~
（1）统计离散数学成绩分布
CREATE TABLE SCC( Grades CHAR(5),
Num INT
) --存人数
INSERT INTO SCC(Grades,Num)
VALUES('>90',0);
INSERT INTO SCC(Grades,Num)
VALUES('>80',0);
INSERT INTO SCC(Grades,Num)
VALUES('>70',0)
2022-05-20 09:44:39
489KB
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3.定义并理解下列术语，说明它们之间的联系与区别：
（1）域（domain）：域是一组具有相同数据类型的集合。
笛卡尔积（cartesian product）：域上的一种集合运算。
给定一组域D1，D2，…，Dn，允许其中某些域是相同的。D1，D2，…，Dn的笛卡尔积为:D1×D2×…×Dn＝｛（d1，d2，…，dn）｜diÎDi，i＝1，2，…，n｝。
关系（relation）：D1×D2×…×Dn的子集叫作在域D1，D2，…，Dn上的关系，表示为R（D1，D2，…，Dn）。 R：关系名，n：关系的目或度。
元组（Tuple）：笛卡尔积中每一个元素叫作一个n元组。
属性：候选码的诸属性称为主
2022-03-20 23:48:00
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资源包括：19道SQL语句查询题目及答案、建表SQL语句、题目相关的表截图。答案中除了包含intersect、except关键词的答案，其余都在MySQL上跑过，确保运行无误（MySQL不支持intersect、except关键词），因为脑细胞死得有些多，资源分不少请大家见谅。
题目如下：
Q:Find all customers who have both an account and a loan at the Perryridge branch.(ps:MySQL不支持intersect运算符)
Q:Find the number of depositors for each branch.
Q:Find the names of all branches where the average account balance is more than $1,200.
Q:Find the names of all branches that have greater assets than all branches located in Brooklyn.
Q:Find all accounts with the maximum balance.
Q:Find all branches that have greater assets than some branch located in Brooklyn.
Q:Find all customers who have both an account and a loan at the bank.
Q:Find all customers who have accounts at all branches located in Brooklyn.
Q:Find the average account balance at the Perryridge branch.
Q:Find the number of tuples in the customer relation.
Q:Find the number of depositors in the bank.
Q:Find the number of depositors for each branch.
Q:Find all customers who have a loan at the bank but do not have an account at the bank.
Q:Find all branches where the total account deposit is greater than the average of the total account deposits at all branches.
Q:Find all customers who have both an account and a loan at the bank.
Q:Find all customers who have at most one account at the Perryridge branch.
Q:Provide as a gift for all loan customers of the Perryridge branch, a $200 savings account. Let the loan number serve as the account number for the new savings account.
Q:Increase all accounts with balances over $10,000 by 6%, all other accounts receiver 5%.
2022-03-16 19:51:17
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