找一个能创建文件路径的函数，文件夹路径如下这些每一层级都不存在，要兼容windows和linux
d:/a/b/c/d/e/f
d:\a\b\c\d\e\f
/a/b/c/d/e/fg/h
```c++
cpp
#include <iostream>
#include <string>
#include <filesystem>
#ifdef _WIN32
const char PATH_SEPARATOR = '\\';
#else
const char PATH_SEPARATOR = '/';
#endif
bool create_directory(const std::string& path)
{
std::filesystem::path dir_path(path);
bool success = std::filesystem::create_directories(dir_path);
return success;
}
int main()
{
std::string path = "d:/a/b/c/d/e/f"; // or d:\\a\\b\\c\\d\\e\\f on Windows
path += PATH_SEPARATOR + "g" + PATH_SEPARATOR + "h";
bool success = create_directory(path);
if (success)
{
std::cout << "Directory created: " << path << std::endl;
}
else
{
std::cerr << "Failed to create directory: " << path << std::endl;
}
return 0;
}
该函数使用std::filesystem::create_directories()函数创建目录路径，该函数在C++17中引入，并根据需要创建目录。如果目录已经存在，则不会引发错误。
为了使该函数兼容Windows和Linux，我们定义一个路径分隔符常量PATH_SEPARATOR，并根据操作系统选择使用反斜杠或正斜杠作为分隔符。
在主函数中，我们将要创建的完整路径存储在字符串变量中，并在其末尾添加新目录名称。然后我们调用create_directory()函数，如果函数成功创建目录，则输出一条消息，否则输出错误消息。
```
不知道你这个问题是否已经解决, 如果还没有解决的话:#include<iostream>
#include<string>
#include<fstream>
using namespace std;
/*一些测试指令
* TABLE LIST
* CREATE TABLE Student FROM student.txt
* CREATE TABLE CS_Student FROM CS.txt
* CREATE TABLE Student (学号,姓名,专业) TO student.txt
* CREATE TBALE Lecture (课程编号,课程名称,任课老师) TO lecture.txt
* DROP TABLE Lecture
*
* INSERT INTO Student VALUES (170000001,张三,计算机科学与技术)
* INSERT INTO Student VALUES (170000002,李四,金融系)
* INSERT INTO Student (学号,姓名) VALUES (170000003,王二)
* INSERT INTO Student (学号,姓名,专业) VALUES (170000004,刘五,微电子)
*
* DELETE FROM Student WHERE 姓名 = 张三
* DELETE * FROM Student
*
* UPDATE Student SET 学号 = 170000000, 专业 = 计算机科学与技术
* UPDATE Student SET 学号 = 170000000, 专业 = 地球科学 WHERE 姓名 = 张三
*
* SELECT 学号,姓名 FROM Student
* SELECT * FROM Student
* SELECT 专业 FROM Student
* SELECT DISTINCT 专业 FROM Student
* SELECT * FROM Student ORDER BY 学号 DESC
* SELECT 专业 FROM Student WHERE 姓名 = 张三
* SELECT * FROM Student WHERE 姓名 = 张三
* SELECT * FROM Student WHERE 专业 = 计算机科学与技术 TO CS.txt
*
* SELECT * FROM Student WHERE 学号 > 170000000
* SELECT MAX(学号) FROM Student
* SELECT * FROM Student WHERE 学号 < (SELECT MAX(学号) FROM Student)
*/
/*
* 这里是数据结构及函数声明~
*/
struct SQL //数据库结构体，包括表名和文件名和表格对应序号
{
string table_name;
string file_name;
int index;
};
SQL my_sql[100]; //维护一个数据库状态数组
int my_sql_num = 0; //当前数据库状态行数
struct TABLE //表格结构体，包括表名，文件名，各列的属性名，行数列数
{
string table_name;
string file_name;
string column[50];
int col_num = 0;
int row_num = 0;
};
TABLE all_table[100]; //维护一个全体表格数组
int table_num = 0; //当前数据库表格数量
string table_data[100][100]; //维护一个数据二维数组，用于暂时存储更新的表格数据
int row = 0, col = 0; //当前表格数据行列数
//读取数据库文件
void read_my_sql();
//写入数据库文件
void write_my_sql();
//读取所有表格及其属性
void read_all_table();
//读取表头
void read_table(int index, string filename);
//写入表头
void write_table(int index, string filename);
//读取表格数据
void read_table_data(int index, string filename);
//写入表格数据
void write_table_data(int index, string filename);
//根据指令创建表格
void Create_table(char ins[]);
//根据指令删除表格
void Drop_table(char ins[]);
//查看所有表格
void Table_list();
//向表格中插入数据
void Insert_table_data(char ins[]);
//删除表格数据
void Delete_table_data(char ins[]);
//修改表格数据
void Updata_table_data(char ins[]);
//选择表格数据并展示
void Selete_table_data(char ins[]);
//打印表格数据
void printf_table(int index);
//打印所有表格列表
void printf_table_list();
//判断是否为空行（即m是否为字母）
bool is_not_endl(char m);
/*
* 这里是主函数~
*/
int main()
{
cout << "\033[33m-----\033[32mWelcome \033[35mto \033[36mmySQL!\033[33m-----\033[0m" << endl;
while (true)
{
cout << "(mysql)==>";
char ins[100]; //用来接受指令
cin.getline(ins, 100);
//Quit 退出数据库
if (ins[0] == 'q'&& ins[1] == 'u'&& ins[2] == 'i'&& ins[3] == 't')
{
cout << "\033[33m-----\033[32mQuit \033[36mmySQL!\033[33m-----\033[0m" << endl;
break;
}
//CREATE TABLE 创建表格功能
else if (ins[0] == 'C' && ins[1] == 'R' && ins[2] == 'E' && ins[3] == 'A' && ins[4] == 'T' && ins[5] == 'E')
{
Create_table(ins);
}
//DROP TABLE 删除表格功能
else if (ins[0] == 'D' && ins[1] == 'R' && ins[2] == 'O' && ins[3] == 'P')
{
Drop_table(ins);
}
//TABLE LIST 查看所有表格
else if ((ins[0]=='0')||(ins[0] == 'T' && ins[1] == 'A' && ins[2] == 'B' && ins[3] == 'L' && ins[4] == 'E'))
{
Table_list();
}
//INSERT INTO 插入数据
else if (ins[0] == 'I' && ins[1] == 'N' && ins[2] == 'S' && ins[3] == 'E' && ins[4] == 'R' && ins[5] == 'T')
{
Insert_table_data(ins);
}
//DELETE 删除数据
else if (ins[0] == 'D' && ins[1] == 'E' && ins[2] == 'L' && ins[3] == 'E' && ins[4] == 'T' && ins[5] == 'E')
{
Delete_table_data(ins);
}
//UPDATE 更新数据
else if (ins[0] == 'U' && ins[1] == 'P' && ins[2] == 'D' && ins[3] == 'A' && ins[4] == 'T' && ins[5] == 'E')
{
Updata_table_data(ins);
}
//SELECT 选择数据
else if (ins[0] == 'S' && ins[1] == 'E' && ins[2] == 'L' && ins[3] == 'E' && ins[4] == 'C' && ins[5] == 'T')
{
Selete_table_data(ins);
}
//ERROR 指令错误
else
{
cout << "Error instruction!" << endl;
}
}
return 0;
}
/*
* 下面是函数的定义~
*/
//读取数据库状态文件
void read_my_sql()
{
my_sql_num = 0; //读入新状态前先将原状态归零
const string my_sql_filename = "my_sql.txt"; //设置数据库状态文件名
//打开文件，若文件不存在，则创建文件
ifstream in_file(my_sql_filename, ios::_Noreplace);
while (in_file.peek() != EOF)
{
in_file >> my_sql[my_sql_num].table_name;
in_file >> my_sql[my_sql_num].file_name;
in_file >> my_sql[my_sql_num].index;
if (is_not_endl(my_sql[my_sql_num].table_name[0]) == 1)
my_sql_num++;
}
in_file.close();
}
//写入数据库状态文件
void write_my_sql()
{
const string my_sql_filename = "my_sql.txt"; //设置数据库状态文件名
ofstream out_file(my_sql_filename, ios::out);
for (int i = 0; i < my_sql_num; i++)
{
//表名 文件名 下标
out_file << my_sql[i].table_name << " ";
out_file << my_sql[i].file_name << " ";
out_file << my_sql[i].index << endl;
}
out_file.close();
}
//读取所有表格及其属性
void read_all_table()
{
table_num = 0; //表格数归零
for (int i = 0; i < my_sql_num; i++)
{
//每读一行数据库信息都会得到一张表
int ind = my_sql[i].index;
all_table[ind].table_name = my_sql[i].table_name;
all_table[ind].file_name = my_sql[i].file_name;
read_table(ind, my_sql[i].file_name);
if (is_not_endl(all_table[ind].file_name[0]) == 1)
table_num++;
}
}
//读取表头
void read_table(int index, string filename)
{
all_table[index].col_num = 0; //读入表头前先将表格列数归零
//打开文件，若文件不存在，则创建文件
ifstream in_file(filename, ios::_Noreplace);
string s;
getline(in_file, s);
int i = 0;
//解析表头
while(i<s.size())
{
int k = 0;
string str;
if (s[i + k] == ' ') //规避汉字中间的两个空格
i++;
while (i+k!=s.size() && s[i + k] != ' ')
{
str += s[i + k];
k++;
}
int c = all_table[index].col_num;
all_table[index].column[c] = str;
all_table[index].col_num++;
i = i + k + 1;
}
in_file.close();
}
//写入表头
void write_table(int index, string filename)
{
ofstream out_file(filename, ios::out);
for (int i = 0; i < all_table[index].col_num; i++)
out_file << all_table[index].column[i] << " ";
out_file << endl;
out_file.close();
}
//读取表格数据
void read_table_data(int index, string filename)
{
all_table[index].row_num = 0; //读入表头前先将表格行数归零
//打开文件，若文件不存在，则创建文件
ifstream in_file(filename, ios::_Noreplace);
//先读表头
string s;
getline(in_file, s);
//剩下的是表格数据
while(in_file.peek()!=EOF)
{
for (int j = 0; j < all_table[index].col_num; j++)
in_file >> table_data[all_table[index].row_num][j]; //用二维数组接受表格信息
if(table_data[all_table[index].row_num][0]>="0" && table_data[all_table[index].row_num][0]<="9")
all_table[index].row_num++;
}
in_file.close();
}
//写入表格数据
void write_table_data(int index, string filename)
{
ofstream out_file(filename, ios::out);
//写入表头
for (int i = 0; i < all_table[index].col_num; i++)
{
out_file << all_table[index].column[i] << " ";
}
out_file << endl;
//写入数据
for (int i = 0; i < all_table[index].row_num; i++)
{
for (int j = 0; j < all_table[index].col_num; j++)
{
out_file << table_data[i][j]<<" ";
}
out_file << endl;
}
out_file.close();
}
//根据指令创建表格，获取表名、文件名、属性名等
void Create_table(char ins[])
{
//先读取数据库状态文件和现有表格列表
read_my_sql();
read_all_table();
//解析指令获取表名，记录到总表格数组中
string tablename;
int i = 13; //移动到指令中name的第一位
while (ins[i] != ' ')
{
tablename += ins[i];
i++;
}
all_table[table_num].table_name = tablename;
i += 1;
//第一类创建语句
if (ins[i] == '(')
{
//检测表格名是否重复
for (int j = 0; j < my_sql_num; j++)
{
if (my_sql[j].table_name == tablename)
{
//表格名已存在
cout << "TABLE " << tablename << " Already Exists !" << endl;
return;
}
}
//解析指令获取每一列的属性名，记录到总表格数组中
i += 1; //移动到指令中column[i]的第一位
int k = 0;
string col_name[50];
col = 0;
while (true)
{
col_name[col] += ins[i + k];
k++;
if (ins[i + k] == ',' || ins[i + k] == '，')
{
//把每列的名字给到对应表格的column数组中，对应列数+1
int c = all_table[table_num].col_num;
all_table[table_num].column[c] = col_name[col];
all_table[table_num].col_num++; col++;
//移动至下一个列名的第一位
i = i + k + 1;
k = 0;
}
else if (ins[i + k] == ')' || ins[i + k] == '）')
{
//把每列的名字给到对应表格的column数组中，对应列数+1
int c = all_table[table_num].col_num;
all_table[table_num].column[c] = col_name[col];
all_table[table_num].col_num++; col++;
i = i + k + 1;
break;
}
}
//解析指令获取文件名，记录到总表格数组中
i += 4; //移动到指令中file的第一位
string filename;
while (ins[i] != '\0')
{
filename += ins[i];
i++;
}
all_table[table_num].file_name = filename;
//创建表格文件并写入表头
write_table(table_num, filename);
//修改数据库状态
my_sql[my_sql_num].table_name = tablename;
my_sql[my_sql_num].file_name = filename;
my_sql[my_sql_num].index = table_num;
my_sql_num++;
write_my_sql(); //更新数据库状态文件
table_num++; //最后，表格数量加一
//展示最新创建的表头
cout << "--------------------" << endl;
cout << "ID ";
for (int i = 0; i < all_table[table_num - 1].col_num; i++)
{
cout << all_table[table_num - 1].column[i] << " ";
}
cout << endl;
cout << "--------------------" << endl;
}
//第二类创建语句（相当于打印已有表格）
else if (ins[i] == 'F')
{
int index;
string filename;
bool flag = 1;
for (int j = 0; j < my_sql_num; j++)
{
if (my_sql[j].table_name == tablename)
{
//找到了对应的表格
index = my_sql[j].index;
filename = my_sql[j].file_name;
read_table_data(index, filename);
printf_table(index);
flag = 0;
break;
}
else if (my_sql[j].table_name == "None")
{
//给无名氏表格命名
my_sql[j].table_name = tablename;
write_my_sql();
index = my_sql[j].index;
filename = my_sql[j].file_name;
read_table_data(index, filename);
printf_table(index);
flag = 0;
break;
}
}
if (flag == 1) //没找到
{
cout << "Not found TABLE " << tablename << " !" << endl;
return;
}
}
else
{
cout << "Error instruction!" << endl;
}
}
//根据指令删除表格
void Drop_table(char ins[])
{
//先读取数据库状态文件和现有表格列表
read_my_sql();
read_all_table();
//解析指令获取待删除表名
string tablename;
int i = 11;
while (ins[i] != '\0')
{
tablename += ins[i];
i++;
}
bool flag = 1;
for (int j = 0; j < my_sql_num;j++)
{
if (my_sql[j].table_name == tablename)
{
//找到待删的表格，则进行数据迁移
for (int k = j; k < my_sql_num-1; k++)
{
my_sql[k].table_name = my_sql[k+1].table_name;
my_sql[k].file_name = my_sql[k+1].file_name;
}
table_num--;
my_sql_num--;
flag = 0;
cout << "DROP TABLE SUCCESS !" << endl;
break;
}
}
if (flag == 1) //没找到
{
cout << "Not found TABLE " << tablename << " !" << endl;
return;
}
write_my_sql(); //更新数据库状态文件
read_all_table(); //修改当前表格列表
}
//查看所有表格
void Table_list()
{
//先读取数据库状态文件和现有表格列表
read_my_sql();
read_all_table();
//依次读取每张表格的数据
for (int i = 0; i < table_num; i++)
{
read_table_data(i, all_table[i].file_name);
}
//打印所有表格信息
cout << " Total table number:" << table_num << endl;
for (int i = 0; i < table_num; i++)
{
cout << " " << all_table[i].table_name << ":";
cout << "（" << all_table[i].col_num << "，" << all_table[i].row_num << "）";
if (all_table[i].col_num == 0)
cout << "[ ]" << endl;
else
{
cout << "[" << all_table[i].column[0];
for (int j = 1; j < all_table[i].col_num; j++)
cout << "，" << all_table[i].column[j];
cout << "]" << endl;
}
}
}
//向表格中插入数据
void Insert_table_data(char ins[])
{
//先读取数据库状态文件和现有表格列表
read_my_sql();
read_all_table();
//解析指令获取表名
string tablename;
int i = 12; //移动到指令中name的第一位
while (ins[i] != ' ')
{
tablename += ins[i];
i++;
}
all_table[table_num].table_name = tablename;
//根据表名打开对应文件，读取表格数据
int index;
string filename;
bool flag = 1;
for (int j = 0; j < my_sql_num; j++)
{
if (my_sql[j].table_name == tablename)
{
//找到了对应的表格
index = my_sql[j].index;
filename = my_sql[j].file_name;
read_table_data(index, filename);
flag = 0;
break;
}
}
if (flag == 1) //没找到
{
cout << "Not found TABLE " << tablename << " !" << endl;
return;
}
i += 1;
//第一类插入语句
if (ins[i] == 'V')
{
i += 8; //i移动到value[i]的第一位
int k = 0;
string col_value[50];
int num = 0;
col = 0, row = all_table[index].row_num;
while (true)
{
col_value[num] += ins[i + k];
k++;
if (ins[i + k] == ',' || ins[i + k] == '，')
{
//把每列的值给到对应表格的值数组中，对应列数+1
table_data[row][col] = col_value[num];
num++; col++;
//移动至下一个值
i = i + k + 1;
k = 0;
}
else if (ins[i + k] == ')' || ins[i + k] == '）')
{
//把每列的值给到对应表格的值数组中，对应列数+1
table_data[row][col] = col_value[num];
num++; col++;
i = i + k + 1;
break;
}
}
cout << "INSERT SUCCESS !" << endl;
all_table[index].row_num++;
printf_table(index);
//修改表格文件
write_table_data(index, filename);
}
//第二类插入语句
else if (ins[i] == '(')
{
//获取给定列名称和添加的值
i += 1; //i移动到column[i]的第一位
int k = 0;
string cols[50]; //暂存column[i]的值
int num = 0; //给定值的个数
while (true)
{
cols[num] += ins[i + k];
k++;
if (ins[i + k] == ',' || ins[i + k] == '，')
{
num++;
//移动至下一个值
i = i + k + 1;
k = 0;
}
else if (ins[i + k] == ')' || ins[i + k] == '）')
{
num++;
i = i + k + 1;
break;
}
}
i += 9; //i移动到value[i]的第一位
k = 0;
string value[50]; //暂存value[i]的值
num = 0; //给定值的个数
while (true)
{
string col_value;
value[num] += ins[i + k];
k++;
if (ins[i + k] == ',' || ins[i + k] == '，')
{
num++;
//移动至下一个值
i = i + k + 1;
k = 0;
}
else if (ins[i + k] == ')' || ins[i + k] == '）')
{
num++;
i = i + k + 1;
break;
}
}
col = 0, row = all_table[index].row_num;
for (int m = 0; m < all_table[index].col_num; m++)
{
bool tag = 1; //表示是否为缺省
for (int n = 0; n < num; n++)
{
if (all_table[index].column[m] == cols[n])
{
table_data[row][m] = value[n];
tag = 0;
break;
}
}
if (tag == 1)
table_data[row][m] = "空"; //缺省值默认为空
}
cout << "INSERT SUCCESS !" << endl;
all_table[index].row_num++;
printf_table(index);
//修改表格文件
write_table_data(index, filename);
}
else
{
cout << "Error instruction!" << endl;
}
}
//删除表格数据
void Delete_table_data(char ins[])
{
//先读取数据库状态文件和现有表格列表
read_my_sql();
read_all_table();
//第一类删除语句
if (ins[7] == 'F')
{
//解析指令获取表名
string tablename;
int i = 12; //移动到指令中name的第一位
while (ins[i] != ' ')
{
tablename += ins[i];
i++;
}
all_table[table_num].table_name = tablename;
//读取表格数据
int index;
string filename;
bool flag = 1;
for (int j = 0; j < my_sql_num; j++)
{
if (my_sql[j].table_name == tablename)
{
//找到了对应的表格
index = my_sql[j].index;
filename = my_sql[j].file_name;
read_table_data(index, filename);
flag = 0;
break;
}
}
if (flag == 1) //没找到
{
cout << "Not found TABLE " << tablename << " !" << endl;
return;
}
i += 7; //i移动到待删除的column第一位
string column;
while (ins[i] != ' ')
{
column += ins[i];
i++;
}
i += 3; //i移动到待删除的value第一位
string value;
while (ins[i] != '\0')
{
value += ins[i];
i++;
}
col = all_table[index].col_num, row = all_table[index].row_num;
//先找到删除的列的下标
int column_index = -1;
for (int k = 0; k < col; k++)
{
if (all_table[index].column[k] == column)
{
column_index = k;
break;
}
}
if (column_index == -1)
{
cout << "Error instruction!" << endl;
return;
}
bool tag = 1;
//再逐行搜索满足条件的记录
for (int k = 0; k < row; k++)
{
if (table_data[k][column_index] == value)
{
tag = 0;
//找到待删行，进行数据迁移
for (int m = k; m < row - 1; m++)
{
for (int n = 0; n < col; n++)
{
table_data[m][n] = table_data[m + 1][n];
}
}
break;
}
}
if (tag == 1)
{
cout << "Error instruction!" << endl;
return;
}
else
{
all_table[index].row_num--;
cout << "DELETE SUCCESS !" << endl;
printf_table(index);
//修改表格文件
write_table_data(index, filename);
}
}
//第二类删除语句
else if (ins[7] == '*' && ins[9]=='F')
{
//解析指令获取表名
string tablename;
int i = 14; //移动到指令中name的第一位
while (ins[i] != '\0')
{
tablename += ins[i];
i++;
}
all_table[table_num].table_name = tablename;
//读取表格数据
int index;
string filename;
bool flag = 1;
for (int j = 0; j < my_sql_num; j++)
{
if (my_sql[j].table_name == tablename)
{
//找到了对应的表格
index = my_sql[j].index;
filename = my_sql[j].file_name;
read_table_data(index, filename);
flag = 0;
break;
}
}
if (flag == 1) //没找到
{
cout << "Not found TABLE " << tablename << " !" << endl;
return;
}
all_table[index].row_num = 0; //删除所有行
cout << "DELETE SUCCESS !" << endl;
printf_table(index);
//修改表格文件
write_table_data(index, filename);
}
else
{
cout << "Error instruction!" << endl;
}
}
//修改表格数据
void Updata_table_data(char ins[])
{
//先读取数据库状态文件和现有表格列表
read_my_sql();
read_all_table();
//解析指令获取表名
string tablename;
int i = 7; //移动到指令中name的第一位
while (ins[i] != ' ')
{
tablename += ins[i];
i++;
}
all_table[table_num].table_name = tablename;
//根据表名打开对应文件，读取表格数据
int index;
string filename;
bool flag = 1;
for (int j = 0; j < my_sql_num; j++)
{
if (my_sql[j].table_name == tablename)
{
//找到了对应的表格
index = my_sql[j].index;
filename = my_sql[j].file_name;
read_table_data(index, filename);
flag = 0;
break;
}
}
if (flag == 1) //没找到
{
cout << "Not found TABLE " << tablename << " !" << endl;
return;
}
i += 5; //移动到column i第一位
int k = 0;
int tag = 0;
string s[50];
string column[50], value[50];
int num = 0;
while (true)
{
while (ins[i + k] != ','&& ins[i + k] != '\0'&&ins[i + k] != 'W')
{
s[num] += ins[i + k];
k++;
}
if (ins[i + k] == ',')
{
num++;
i = i + k + 2;
k = 0;
}
else if (ins[i + k] == '\0')
{
tag = 1; //第一类更新语句
num++;
break;
}
else if (ins[i + k] == 'W')
{
tag = 2; //第二类更新语句
num++;
//最后一句多了一个空格，删去之
string temp = s[num - 1].substr(0, s[num - 1].size() - 1);
s[num - 1] = temp;
i = i + k + 6; //i 移动到column首位
break;
}
}
//逐句再次解析
for (int j = 0; j < num; j++)
{
int cur = 0;
while (s[j][cur] != ' ')
cur++;
column[j] = s[j].substr(0, cur);
cur += 3;
value[j] = s[j].substr(cur, s[j].size());
}
if (tag == 1)
{
//对表格每一列进行遍历，搜索column[]数组判断是否需要更改
for (int j = 0; j < all_table[index].col_num; j++)
{
for (int n = 0; n < num; n++)
{
if (all_table[index].column[j] == column[n])
{
//更改这一列每一行的值
for (int m = 0; m < all_table[index].row_num; m++)
{
//m是表格的某一行，j是表格的某一列，n是对应要修改的值
table_data[m][j] = value[n];
}
break;
}
}
}
cout << "UPDATE SUCCESS !" << endl;
printf_table(index);
//修改表格文件
write_table_data(index, filename);
}
else if (tag == 2)
{
//记录限制条件 column = value
string clmn, val;
while (ins[i] != ' ')
{
clmn += ins[i];
i++;
}
i += 3;
while (ins[i] != '\0')
{
val += ins[i];
i++;
}
//找到对应的列的下标
int column_index = -1;
for (k = 0; k < all_table[index].col_num; k++)
{
if (all_table[index].column[k] == clmn)
{
column_index = k;
break;
}
}
if (column_index == -1)
{
cout << "Error instruction!" << endl;
return;
}
//对表格每一列进行遍历，搜索column[]数组判断是否需要更改
for (int j = 0; j < all_table[index].col_num; j++)
{
for (int n = 0; n < num; n++)
{
if (all_table[index].column[j] == column[n])
{
//只更改这一列满足限制条件的行的值
for (int m = 0; m < all_table[index].row_num; m++)
{
//判断是否满足条件
if (table_data[m][column_index] == val)
{
//m是表格的某一行，j是表格的某一列，n是对应要修改的值
table_data[m][j] = value[n];
}
}
break;
}
}
}
cout << "UPDATE SUCCESS !" << endl;
printf_table(index);
//修改表格文件
write_table_data(index, filename);
}
else
{
cout << "Error instruction!" << endl;
}
}
//选择表格数据并展示
void Selete_table_data(char ins[])
{
//先读取数据库状态文件和现有表格列表
read_my_sql();
read_all_table();
if (ins[7] == '*')
{
//解析指令获取表名
string tablename;
int i = 14; //移动到指令中name的第一位
while (ins[i] != '\0' && ins[i] != ' ')
{
tablename += ins[i];
i++;
}
//根据表名打开对应文件，读取表格数据
int index;
string filename;
bool flag = 1;
for (int j = 0; j < my_sql_num; j++)
{
if (my_sql[j].table_name == tablename)
{
//找到了对应的表格
index = my_sql[j].index;
filename = my_sql[j].file_name;
read_table_data(index, filename);
flag = 0;
break;
}
}
if (flag == 1) //没找到
{
cout << "Not found TABLE " << tablename << " !" << endl;
return;
}
//从TABLE name里选择所有列展示，即展示整个TABLE
if (ins[i] == '\0')
{
printf_table(index);
}
//对返回的查询结果按某些列进行排序展示
else if (ins[i] == ' ' && ins[i + 1] == 'O')
{
i += 10; //移动到 column i 第一位
string column[50];
int num = 0;
int k = 0;
while (true)
{
while (ins[i + k] != ',' && ins[i + k] != ' ')
{
column[num] += ins[i + k];
k++;
}
if (ins[i + k] == ',')
{
num++;
i = i + k + 1;
k = 0;
}
else if (ins[i + k] == ' ')
{
num++;
i = i + k + 1; //i 移动到ASC|DESC首位
break;
}
}
//找到对应的列的下标
int column_index = -1;
for (k = 0; k < all_table[index].col_num; k++)
{
//支持按某一列的值排序
if (all_table[index].column[k] == column[0])
{
column_index = k;
break;
}
}
if (column_index == -1)
{
cout << "Error instruction!" << endl;
return;
}
if (ins[i] == 'A') //升序
{
for (int m = 0; m < all_table[index].row_num - 1; m++)
{
for (int n = 0; n < all_table[index].row_num - m - 1; n++)
{
if (table_data[n][column_index] > table_data[n + 1][column_index])
{
//交换两行元素
for (int tt = 0; tt < all_table[index].col_num; tt++)
{
string temp = table_data[n][tt];
table_data[n][tt] = table_data[n + 1][tt];
table_data[n + 1][tt] = temp;
}
}
}
}
}
else if (ins[i] == 'D') //降序
{
for (int m = 0; m < all_table[index].row_num - 1; m++)
{
for (int n = 0; n < all_table[index].row_num - m - 1; n++)
{
if (table_data[n][column_index] < table_data[n + 1][column_index])
{
//交换两行元素
for (int tt = 0; tt < all_table[index].col_num; tt++)
{
string temp = table_data[n][tt];
table_data[n][tt] = table_data[n + 1][tt];
table_data[n + 1][tt] = temp;
}
}
}
}
}
else
{
cout << "Error instruction!" << endl;
return;
}
//打印
//打印表头
cout << "----------------------------------------" << endl;
cout << "ID ";
for (int j = 0; j < all_table[index].col_num; j++)
{
cout << all_table[index].column[j] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
//打印数据
for (int m = 0; m < all_table[index].row_num; m++)
{
cout << m + 1 << " ";
for (int n = 0; n < all_table[index].col_num; n++)
{
cout << table_data[m][n] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
}
}
else if (ins[i] == ' ' && ins[i + 1] == 'W')
{
i += 7; //i 移动到column第一位
//记录限制条件 column = value
string clmn, val;
while (ins[i] != ' ')
{
clmn += ins[i];
i++;
}
i += 1;
// column = value
if (ins[i] == '=')
{
i += 2;
while (ins[i] != '\0' && ins[i] != ' ')
{
val += ins[i];
i++;
}
//找到对应的列的下标
int column_index = -1;
for (int k = 0; k < all_table[index].col_num; k++)
{
if (all_table[index].column[k] == clmn)
{
column_index = k;
break;
}
}
if (column_index == -1)
{
cout << "Error instruction!" << endl;
return;
}
if (ins[i] == '\0')
{
//打印
//打印表头
cout << "----------------------------------------" << endl;
cout << "ID ";
for (int j = 0; j < all_table[index].col_num; j++)
{
cout << all_table[index].column[j] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
//打印数据
for (int m = 0; m < all_table[index].row_num; m++)
{
if (table_data[m][column_index] == val)
{
cout << m + 1 << " ";
for (int n = 0; n < all_table[index].col_num; n++)
{
cout << table_data[m][n] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
}
}
}
else
{
i += 4; //移动到新表格文件名第一位
string new_filename;
while (ins[i] != '\0')
{
new_filename += ins[i];
i++;
}
//打印
//打印表头
cout << "----------------------------------------" << endl;
cout << "ID ";
for (int j = 0; j < all_table[index].col_num; j++)
{
cout << all_table[index].column[j] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
//打印数据
for (int m = 0; m < all_table[index].row_num; m++)
{
if (table_data[m][column_index] == val)
{
cout << m + 1 << " ";
for (int n = 0; n < all_table[index].col_num; n++)
{
cout << table_data[m][n] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
}
}
//创建新表写入文件
ofstream out_file(new_filename, ios::out);
//写入表头
for (int j = 0; j < all_table[index].col_num; j++)
{
out_file << all_table[index].column[j] << " ";
}
out_file << endl;
//写入数据
for (int m = 0; m < all_table[index].row_num; m++)
{
if (table_data[m][column_index] == val)
{
for (int n = 0; n < all_table[index].col_num; n++)
{
out_file << table_data[m][n] << " ";
}
out_file << endl;
}
}
out_file.close();
//修改数据库状态
my_sql[my_sql_num].table_name = "None";
my_sql[my_sql_num].file_name = new_filename;
my_sql[my_sql_num].index = table_num;
my_sql_num++;
write_my_sql(); //更新数据库状态文件
}
}
// column > value
else if (ins[i] == '>')
{
i += 2;
while (ins[i] != '\0')
{
val += ins[i];
i++;
}
//找到对应的列的下标
int column_index = -1;
for (int k = 0; k < all_table[index].col_num; k++)
{
if (all_table[index].column[k] == clmn)
{
column_index = k;
break;
}
}
if (column_index == -1)
{
cout << "Error instruction!" << endl;
return;
}
//打印
//打印表头
cout << "----------------------------------------" << endl;
cout << "ID ";
for (int j = 0; j < all_table[index].col_num; j++)
{
cout << all_table[index].column[j] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
//打印数据
for (int m = 0; m < all_table[index].row_num; m++)
{
if (table_data[m][column_index] > val)
{
cout << m + 1 << " ";
for (int n = 0; n < all_table[index].col_num; n++)
{
cout << table_data[m][n] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
}
}
}
// column < value ，其中value=max(学号)
else if (ins[i] == '<')
{
i += 2;
//找到对应的列的下标
int column_index = -1;
for (int k = 0; k < all_table[index].col_num; k++)
{
if (all_table[index].column[k] == clmn)
{
column_index = k;
break;
}
}
if (column_index == -1)
{
cout << "Error instruction!" << endl;
return;
}
//找学号最大值
string max = table_data[0][column_index];
for (int j = 0; j < all_table[index].row_num; j++)
{
if (table_data[j][column_index] > max)
{
max = table_data[j][column_index];
}
}
//打印
//打印表头
cout << "----------------------------------------" << endl;
cout << "ID ";
for (int j = 0; j < all_table[index].col_num; j++)
{
cout << all_table[index].column[j] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
//打印数据
for (int m = 0; m < all_table[index].row_num; m++)
{
if (table_data[m][column_index] < max)
{
cout << m + 1 << " ";
for (int n = 0; n < all_table[index].col_num; n++)
{
cout << table_data[m][n] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
}
}
}
else
{
cout << "Error instruction!" << endl;
return;
}
}
else
{
cout << "Error instruction!" << endl;
}
}
else if (ins[7] == 'D')
{
string column[50];
int num = 0;
int i = 16; //移动到 column i 第一位
int k = 0;
while (true)
{
while (ins[i + k] != ',' && ins[i + k] != ' ')
{
column[num] += ins[i + k];
k++;
}
if (ins[i + k] == ',')
{
num++;
i = i + k + 1;
k = 0;
}
else if (ins[i + k] == ' ')
{
num++;
i = i + k + 6; //i 移动到name首位
break;
}
}
//解析表名
string tablename;
while (ins[i] != '\0' && ins[i] != ' ')
{
tablename += ins[i];
i++;
}
//根据表名打开对应文件，读取表格数据
int index;
string filename;
bool tag = 1;
for (int j = 0; j < my_sql_num; j++)
{
if (my_sql[j].table_name == tablename)
{
//找到了对应的表格
index = my_sql[j].index;
filename = my_sql[j].file_name;
read_table_data(index, filename);
tag = 0;
break;
}
}
if (tag == 1) //没找到
{
cout << "Not found TABLE " << tablename << " !" << endl;
return;
}
bool flag[50]; //给每一列做标记
for (int j = 0; j < all_table[index].col_num; j++)
{
flag[j] = 0;
}
for (int j = 0; j < all_table[index].col_num; j++)
{
for (k = 0; k < num; k++)
{
if (all_table[index].column[j] == column[k])
{
flag[j] = 1;
break;
}
}
}
//打印表头
cout << "----------------------------------------" << endl;
cout << "ID ";
for (int j = 0; j < all_table[index].col_num; j++)
{
if (flag[j] == 1)
cout << all_table[index].column[j] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
//打印数据
for (int m = 0; m < all_table[index].row_num; m++)
{
bool print = 1; //判断要不要打印
for (int n = 0; n < all_table[index].col_num; n++)
{
if (flag[n] == 1)
{
for (int a = 0; a < m; a++)
{
if (table_data[a][n] == table_data[m][n])
{
print = 0;
break;
}
}
}
}
if (print == 1)
{
cout << m + 1 << " ";
for (int n = 0; n < all_table[index].col_num; n++)
{
if (flag[n] == 1)
cout << table_data[m][n] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
}
}
}
else if (ins[7] == 'M')
{
int i = 11;
string column;
while (ins[i] != ')')
{
column += ins[i];
i++;
}
//解析指令获取表名
i += 7;
string tablename;
while (ins[i] != '\0')
{
tablename += ins[i];
i++;
}
//根据表名打开对应文件，读取表格数据
int index;
string filename;
bool flag = 1;
for (int j = 0; j < my_sql_num; j++)
{
if (my_sql[j].table_name == tablename)
{
//找到了对应的表格
index = my_sql[j].index;
filename = my_sql[j].file_name;
read_table_data(index, filename);
flag = 0;
break;
}
}
if (flag == 1) //没找到
{
cout << "Not found TABLE " << tablename << " !" << endl;
return;
}
//找到对应的列的下标
int column_index = -1;
for (int k = 0; k < all_table[index].col_num; k++)
{
if (all_table[index].column[k] == column)
{
column_index = k;
break;
}
}
if (column_index == -1)
{
cout << "Error instruction!" << endl;
return;
}
//找最大值
int maxline = 0;
string max = table_data[0][column_index];
for (int j = 0; j < all_table[index].row_num; j++)
{
if (table_data[j][column_index] > max)
{
max = table_data[j][column_index];
maxline = j;
}
}
//打印
//打印表头
cout << "----------------------------------------" << endl;
cout << "ID ";
for (int j = 0; j < all_table[index].col_num; j++)
{
cout << all_table[index].column[j] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
//打印数据
cout << maxline + 1 << " ";
for (int n = 0; n < all_table[index].col_num; n++)
{
cout << table_data[maxline][n] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
}
else
{
string column[50];
int num = 0;
int i = 7; //移动到 column i 第一位
int k = 0;
while (true)
{
while (ins[i + k] != ',' && ins[i + k] != ' ')
{
column[num] += ins[i + k];
k++;
}
if (ins[i + k] == ',')
{
num++;
i = i + k + 1;
k = 0;
}
else if (ins[i + k] == ' ')
{
num++;
i = i + k + 6; //i 移动到name首位
break;
}
}
//解析表名
string tablename;
while (ins[i] != '\0' && ins[i] != ' ')
{
tablename += ins[i];
i++;
}
all_table[table_num].table_name = tablename;
//根据表名打开对应文件，读取表格数据
int index;
string filename;
bool tag = 1;
for (int j = 0; j < my_sql_num; j++)
{
if (my_sql[j].table_name == tablename)
{
//找到了对应的表格
index = my_sql[j].index;
filename = my_sql[j].file_name;
read_table_data(index, filename);
tag = 0;
break;
}
}
if (tag == 1) //没找到
{
cout << "Not found TABLE " << tablename << " !" << endl;
return;
}
bool flag[50]; //给每一列做标记
for (int j = 0; j < all_table[index].col_num; j++)
{
flag[j] = 0;
}
for (int j = 0; j < all_table[index].col_num; j++)
{
for (k = 0; k < num; k++)
{
if (all_table[index].column[j] == column[k])
{
flag[j] = 1;
break;
}
}
}
//从TABLE name里选择若干列展示
if (ins[i] == '\0')
{
//打印表头
cout << "----------------------------------------" << endl;
cout << "ID ";
for (int j = 0; j < all_table[index].col_num; j++)
{
if(flag[j]==1)
cout << all_table[index].column[j] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
//打印数据
for (int m = 0; m < all_table[index].row_num; m++)
{
cout << m + 1 << " ";
for (int n = 0; n < all_table[index].col_num; n++)
{
if (flag[n] == 1)
cout << table_data[m][n] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
}
}
//从TABLE name里选择若干列展示
else if (ins[i] == ' ' && ins[i + 1] == 'W')
{
i += 7; //移动到column首位
//记录限制条件 column = value
string clmn, val;
while (ins[i] != ' ')
{
clmn += ins[i];
i++;
}
i += 3;
while (ins[i] != '\0')
{
val += ins[i];
i++;
}
//找到对应的列的下标
int column_index = -1;
for (k = 0; k < all_table[index].col_num; k++)
{
if (all_table[index].column[k] == clmn)
{
column_index = k;
break;
}
}
if (column_index == -1)
{
cout << "Error instruction!" << endl;
return;
}
//打印表头
cout << "----------------------------------------" << endl;
cout << "ID ";
for (int j = 0; j < all_table[index].col_num; j++)
{
if (flag[j] == 1)
cout << all_table[index].column[j] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
//打印数据
for (int m = 0; m < all_table[index].row_num; m++)
{
if(table_data[m][column_index]==val)
{
cout << m + 1 << " ";
for (int n = 0; n < all_table[index].col_num; n++)
{
if (flag[n] == 1)
cout << table_data[m][n] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
}
}
}
else
{
cout << "Error instruction!" << endl;
}
}
}
//打印表格
void printf_table(int index)
{
cout << "----------------------------------------" << endl;
cout << "ID ";
for (int i = 0; i < all_table[index].col_num; i++)
{
cout << all_table[index].column[i] << " ";
}
cout << endl;
cout << "----------------------------------------" << endl;
for (int i = 0; i < all_table[index].row_num; i++)
{
cout << i + 1 << " ";
for (int j = 0; j < all_table[index].col_num; j++)
cout << table_data[i][j] << " ";
cout << endl;
cout << "----------------------------------------" << endl;
}
}
//打印所有表格列表
void printf_table_list()
{
for (int i = 0; i < table_num; i++)
cout << all_table[i].table_name << " " << all_table[i].file_name << endl;
}
//判断是否为空行（即m是否为字母）
bool is_not_endl(char m)
{
if (((m >= 'a') && (m <= 'z')) || ((m >= 'A') && (m <= 'Z')))
return true;
return false;
}