das.txt

模拟数据库系统的各种功能

#include "iostream"
#include "string"
#include "iomanip"
#include "stdlib.h"
#include "fstream"
using namespace std;

struct item
{
	string name;
	string type;
};
struct seq
{
	item *t[10];
	int num;
	string name;
	seq *next;
	seq *follow;
};

int N;
seq *head;
void showFunction()
{
	cout <<"输入功能"<<endl;
	cout <<"create"<<endl<<"insert"<<endl<<"delete"<<endl<<"modify"<<endl<<"charu"<<endl<<"show"<<endl<<"exit"<<endl;
}

void showTable()
{
	string name;
	seq *r,*s;
	
	r = head->follow;
	while(r!=NULL)
	{
		cout <<"表名为：";
		cout <<r->name<<endl;
		N = r->num;
		s = r;
		while(s->next!=NULL)
		{
			int n = 0;
			while(n!=N)
			{
				if(s->next->t[n])
					cout <<s->next->t[n]->name<<setw(10);
				else 
					cout <<"空"<<setw(10);
				n++;
			}
			cout <<endl;
			s = s->next;
		}
		r = r->follow;
	}
	cout <<"没有表了"<<endl;
}


void create()			//////见表
{
	string tName;int n=0;
	seq *newhead = new seq;
	seq *t = new seq;
	cout<<"输入表名"<<endl;
	cin >>tName;				
	
	newhead->name = tName;
	cout <<"输入属性个数(第一个参数是主键)"<<endl;
	cin >>N;
	newhead->num = N;

	newhead->next = t;
	string type,vName;
	while(n!=N)
	{
		t->t[n] = new item;
		cout <<"输入类型"<<endl;
		cin >>type;
		t->t[n]->type = type;
		cout <<"输入变量名"<<endl;
		cin >>vName;
		t->t[n]->name = vName;
		n++;
	}
	t->next = NULL;

	seq *r;
	r = head;
	while(r->follow)
		r = r->follow;
	r->follow = newhead;
	r = newhead;
	r->follow = NULL;
}
void insert()
{
	string tName;
	cout <<"输入要添加数据的表名";
	cin >>tName;

	int n=0;
	seq *temp;
	
	temp = head->follow;
	while(tName!=temp->name&&temp->follow)
		temp = temp->follow;
	if(tName==temp->name)
	{	
		N = temp->num;
		seq *r,*s;
		r = temp;
		while(r->next)
			r = r->next;
		s = new seq;

		cout <<"输入数据"<<endl;
		string name;
		while(n!=N)
		{
			s->t[n] = new item;
			cin >>name;
			s->t[n]->name = name;
			n++;
		}
		
		r->next = s;
		r = s;
		r->next = NULL;
	}
	else
		cout <<"无此表"<<endl;
}

void del()
{
	string tName;
	cout <<"要删除的表名"<<endl;
	cin >>tName;

	seq *r,*s;
	r = head->follow;

	while(r->name!=tName&&r->follow)
		r = r->follow;
	if(r->name==tName)
	{
		int n;s = r->next;int flag;
		cout <<"1.删除属性"<<endl<<"2.删除数据"<<endl;
		cin >>flag;
		if(flag==2)
		{
			cout<<"要删除第几行数据"<<endl;
			cin >>n;
			while(n-1)
			{
				s = s->next;
				n--;
			}
			s->next = s->next->next;
		}
		else if(flag==1)
		{
			cout <<"要删除第几个属性 "<<endl;
			cin >>n;
			s = r->next;
			while(s)
			{
				if(n<r->num)
				{	s->t[n-1]->name = s->t[n]->name;
				}
				s = s->next;
			}
			r->num--;
		}
	}
	else
		cout <<"无此表"<<endl;
}

void modify()
{
	string tName;
	cout <<"要插入的表名"<<endl;
	cin >>tName;

	seq *r,*s;
	r = head->follow;

	while(r->name!=tName&&r->follow)
		r = r->follow;
	if(r->name==tName)
	{
		int flag=0;
		cout <<"1、插入属性"<<endl<<"2、插入数据"<<endl;
		cin >>flag;
		if(flag==2)
		{
			int n;s = r->next;
			cout<<"要插入到第几行之后"<<endl;
			cin >>n;
			while(n-1)
			{
				s = s->next;
				n--;
			}
			cout <<"输入数据"<<endl;

			N = r->num;int t = 0;
			seq *newins = new seq;
			while(t!=N)
			{
				newins->t[t] = new item;
				cin >>newins->t[t]->name;
				t++;
			}
			newins->next = s->next;
			s->next = newins;
		}
		else if(flag==1)
		{
			string newName,newType;
			s = r->next;
			s->t[r->num] = new item;
			cout <<"输入属性类型"<<endl;
			cin >>newType;
			cout <<"输入属性名"<<endl;
			cin >>newName;
			s->t[r->num]->type = newType;
			s->t[r->num]->name = newName;
			r->num++;
			cout <<"一次输入数据"<<endl;
			while(s->next)
			{
				s = s->next;
				s->t[r->num-1] = new item;
				cin >>s->t[r->num-1]->name;
			}
		}
		else 
			cout <<"书入错误"<<endl;
/*		string ins;
		cout <<"输入要插入的位置(在那个主键之后)"<<endl;
		cin >>ins;
		while(ins!=r->t[n]->name&&r->next)
			temp = temp->next;
		seq *newins = new seq;
		cout <<"输入数据"<<endl;
		string name;
		while(n!=N)
		{
			newins->t[n] = new item;
			cin >>name;
			newins->t[n]->name = name;
			n++;
		}
		newins->next = temp->next->next;
		temp->next = newins;
*/	}
	else
		cout <<"无此表"<<endl;
}

void charu()
{
	string tName;
	cout <<"要修改的表名"<<endl;
	cin >>tName;

	seq *r,*s;
	r = head->follow;

	while(r->name!=tName&&r->follow)
		r = r->follow;
	if(r->name==tName)
	{
		int n,n2;s = r->next;string xiu;
		cout<<"要修改到第几行,包括属性行"<<endl;
		cin >>n;
		cout <<"要修改的第几个数据"<<endl;
		cin >>n2;
		cout <<"输入要修改后的数据"<<endl;
		cin >>xiu;
		while(n-1)
		{
			s = s->next;
			n--;
		}
		s->t[n2-1]->name=xiu;
	}
	else
		cout <<"无此表"<<endl;
}
void fileWrite(ofstream& fw)
{
	seq *s,*r;
	r = head;
	while(r->follow)
	{
		int n=0;
		r = r->follow;
		fw <<r->name<<setw(10)<<r->num<<endl;

		s = r->next;
		while(s)
		{
			n =0;
			while(n!=r->num)
			{
				fw <<s->t[n]->type<<setw(5)<<s->t[n]->name<<setw(10);
				n++;
			}
			fw <<endl;
			s = s->next;
		}
	}
}

void choose(ofstream& fw,ifstream& fr)
{
	string ch;
	while(1)
	{
		showFunction();
		cin >>ch;
		if(ch == "create")
			create();
		else if(ch == "insert")
			insert();
		else if(ch == "delete")
			del();
		else if(ch == "modify")
			modify();
		else if(ch == "charu")
			charu();
		else if(ch == "show")
			showTable();
		else if(ch == "exit")
		{fileWrite(fw);	exit(0);}
		else
			cout <<"正确输入"<<endl;		
	}
}

void fileRead(ifstream& fr)
{
	string parameter;int n=0;
	fr >>parameter;
	seq *s,*t;
	t = new seq;
	head->next = t;

	t->name = parameter;
	fr >>N;
	t->num = N;

	while(!fr.fail())
	{
		s = new seq;
		s->t[n] = new item;
		while(n!=N)
		{
			fr >>parameter;
			s->t[n]->name = parameter;
			fr >>parameter;
			s->t[n]->type = parameter;
			t->next = s;
			t = s;
			n++;
		}
	}
	t->next = NULL;
}
int main()
{
//	system("mkdir E:\\stu");
	ifstream fr("output.txt");
	head = new seq;
	head->follow = NULL;
	head->next = NULL;
	if(fr.fail())
		cout<<"文件不存在"<<endl;
//	else
//		fileRead(fr);
	ofstream fw("output.txt");
	choose(fw,fr);
	fw.close();
	fr.close();
	return -1;
}