目錄

前言

項目介紹

功能實現

重要說明

源代碼分享

寫在最后

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前言

程設實驗終于收工了！🎉

終于到了本學期最后一個項目，可謂是一波三折：剛拿到項目要求時認為只是項目二的網店+LINUX操作系統，very easy；中間遇到文件讀寫的bug，苦苦找不到對策，整整一周幾乎沒有進展；最后兩天靈感迸發，修復了之前的bug，并一天碼了破千行代碼，掉了滿地頭發……無論如何，項目終歸是結束了，也留給了我日后繼續學習數據庫和操作系統的基礎，再說回程設實驗，不得不說這門課耗時只能用恐怖形容，所幸下一屆學弟學妹們不用再受這苦😭

最后只想說一句：程設實驗，再nm的見！

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項目介紹

本項目中我們需要在Linux環境下使用C/C++語言搭建一個最簡單、最基礎的數據庫mySQL，模擬數據庫的基本操作，實現六大類基本命令語句，待解決的問題有：

1. 如何實現Linux環境下代碼的編譯與執行（注意Linux和Windows環境下文件操作的不同）；

2. 如何(使用正則表達式)解析指令，獲取不同的操作對象；

3. 如何使用文件保存各個表格的內容以及維護整個數據庫的狀態；

4….

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功能實現

本項目中只要求實現一個最簡單的數據庫，也即實現六大類基本功能——

CREATE TABLE，DROP TABLE，INSERT INTO，DELETE，UPDATE，SELECT

它們對應的命令語句如下：

CREATE TABLE name (column1,column2,···,columnT) TO file

CREATE TABLE name FROM filename

DROP TABLE name

TABLE LIST

INSERT INTO name VALUES (value1,value2,···,valueT)

INSERT INTO name (column1,column2,···) VALUES (value1,value2,···)

DELETE FROM name WHERE column = value

DELETE * FROM name

UPDATE name SET column1 = value1, column2 = value2, ···

UPDATE name SET column1 = value1, column2 = value2, ··· WHERE column = value

SELECT column1,column2,··· FROM name

SELECT * FROM name

SELECT DISTINCT column1,column2,··· FROM name

SELECT * FROM name ORDER BY column1,column2,··· ASC|DESC

SELECT column1,column2,··· FROM name WHERE column = value

SELECT column1,column2,··· FROM name TO file

接下來展示部分命令功能的實現截圖：??

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重要說明

• 正規數據庫的命令解析還是應當考慮正則表達式，本項目中由于時間原因直接使用原始的字符串解析方法，非常暴力，有待改進
• 為了盡可能減少bug，文件名最好采用英文
• Linux環境下可能出現小部分字符亂碼現象，但基礎功能均可正常實現
• 源碼開源 ≠ 完全開放，代碼分享僅供學習工作交流使用，嚴禁作業抄襲及商業用途
• 致謝NJU最后一屆程設實驗課的老師與助教，耐心解答了我的許多問題

接下來分享源代碼！接近兩千行，時間原因不能注釋詳盡，之后有時間爭取補上（有時間也不一定🙄）

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源代碼分享

#include<iostream> #include<string> #include<fstream> using namespace std;/*一些測試指令 * TABLE LIST * CREATE TABLE Student FROM student.txt * CREATE TABLE CS_Student FROM CS.txt * CREATE TABLE Student (學號,姓名,專業) TO student.txt * CREATE TBALE Lecture (課程編號,課程名稱,任課老師) TO lecture.txt * DROP TABLE Lecture * * INSERT INTO Student VALUES (170000001,張三,計算機科學與技術) * INSERT INTO Student VALUES (170000002,李四,金融系) * INSERT INTO Student (學號,姓名) VALUES (170000003,王二) * INSERT INTO Student (學號,姓名,專業) VALUES (170000004,劉五,微電子) * * DELETE FROM Student WHERE 姓名 = 張三 * DELETE * FROM Student * * UPDATE Student SET 學號 = 170000000, 專業 = 計算機科學與技術 * UPDATE Student SET 學號 = 170000000, 專業 = 地球科學 WHERE 姓名 = 張三 * * SELECT 學號,姓名 FROM Student * SELECT * FROM Student * SELECT 專業 FROM Student * SELECT DISTINCT 專業 FROM Student * SELECT * FROM Student ORDER BY 學號 DESC * SELECT 專業 FROM Student WHERE 姓名 = 張三 * SELECT * FROM Student WHERE 姓名 = 張三 * SELECT * FROM Student WHERE 專業 = 計算機科學與技術 TO CS.txt * * SELECT * FROM Student WHERE 學號 > 170000000 * SELECT MAX(學號) FROM Student * SELECT * FROM Student WHERE 學號 < (SELECT MAX(學號) FROM Student) *//* * 這里是數據結構及函數聲明~ */ struct SQL //數據庫結構體，包括表名和文件名和表格對應序號 {string table_name;string file_name;int index; }; SQL my_sql[100]; //維護一個數據庫狀態數組 int my_sql_num = 0; //當前數據庫狀態行數struct TABLE //表格結構體，包括表名，文件名，各列的屬性名，行數列數 {string table_name;string file_name;string column[50];int col_num = 0; int row_num = 0; }; TABLE all_table[100]; //維護一個全體表格數組 int table_num = 0; //當前數據庫表格數量string table_data[100][100]; //維護一個數據二維數組，用于暫時存儲更新的表格數據 int row = 0, col = 0; //當前表格數據行列數//讀取數據庫文件 void read_my_sql();//寫入數據庫文件 void write_my_sql();//讀取所有表格及其屬性 void read_all_table();//讀取表頭 void read_table(int index, string filename);//寫入表頭 void write_table(int index, string filename);//讀取表格數據 void read_table_data(int index, string filename);//寫入表格數據 void write_table_data(int index, string filename);//根據指令創建表格 void Create_table(char ins[]);//根據指令刪除表格 void Drop_table(char ins[]);//查看所有表格 void Table_list();//向表格中插入數據 void Insert_table_data(char ins[]);//刪除表格數據 void Delete_table_data(char ins[]);//修改表格數據 void Updata_table_data(char ins[]);//選擇表格數據并展示 void Selete_table_data(char ins[]);//打印表格數據 void printf_table(int index);//打印所有表格列表 void printf_table_list();//判斷是否為空行（即m是否為字母） bool is_not_endl(char m);/* * 這里是主函數~ */ int main() {cout << "\033[33m-----\033[32mWelcome \033[35mto \033[36mmySQL!\033[33m-----\033[0m" << endl;while (true){cout << "(mysql)==>";char ins[100]; //用來接受指令cin.getline(ins, 100);//Quit 退出數據庫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 創建表格功能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 刪除表格功能 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 插入數據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 刪除數據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 更新數據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 選擇數據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 指令錯誤else{cout << "Error instruction!" << endl;}}return 0; }/* * 下面是函數的定義~ *///讀取數據庫狀態文件 void read_my_sql() {my_sql_num = 0; //讀入新狀態前先將原狀態歸零const string my_sql_filename = "my_sql.txt"; //設置數據庫狀態文件名//打開文件，若文件不存在，則創建文件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(); }//寫入數據庫狀態文件 void write_my_sql() {const string my_sql_filename = "my_sql.txt"; //設置數據庫狀態文件名ofstream out_file(my_sql_filename, ios::out);for (int i = 0; i < my_sql_num; i++){//表名 文件名 下標out_file << my_sql[i].table_name << " ";out_file << my_sql[i].file_name << " ";out_file << my_sql[i].index << endl;}out_file.close(); }//讀取所有表格及其屬性 void read_all_table() {table_num = 0; //表格數歸零for (int i = 0; i < my_sql_num; i++){//每讀一行數據庫信息都會得到一張表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++;} }//讀取表頭 void read_table(int index, string filename) {all_table[index].col_num = 0; //讀入表頭前先將表格列數歸零//打開文件，若文件不存在，則創建文件ifstream in_file(filename, ios::_Noreplace);string s;getline(in_file, s);int i = 0;//解析表頭while(i<s.size()){int k = 0;string str;if (s[i + k] == ' ') //規避漢字中間的兩個空格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(); }//寫入表頭 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(); }//讀取表格數據 void read_table_data(int index, string filename) {all_table[index].row_num = 0; //讀入表頭前先將表格行數歸零//打開文件，若文件不存在，則創建文件ifstream in_file(filename, ios::_Noreplace);//先讀表頭string s;getline(in_file, s);//剩下的是表格數據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]; //用二維數組接受表格信息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(); }//寫入表格數據 void write_table_data(int index, string filename) {ofstream out_file(filename, ios::out);//寫入表頭for (int i = 0; i < all_table[index].col_num; i++){out_file << all_table[index].column[i] << " ";}out_file << endl;//寫入數據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(); }//根據指令創建表格，獲取表名、文件名、屬性名等 void Create_table(char ins[]) {//先讀取數據庫狀態文件和現有表格列表read_my_sql();read_all_table();//解析指令獲取表名，記錄到總表格數組中string tablename;int i = 13; //移動到指令中name的第一位while (ins[i] != ' '){tablename += ins[i];i++;}all_table[table_num].table_name = tablename;i += 1;//第一類創建語句if (ins[i] == '(') {//檢測表格名是否重復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;}}//解析指令獲取每一列的屬性名，記錄到總表格數組中i += 1; //移動到指令中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] == '，'){//把每列的名字給到對應表格的column數組中，對應列數+1int c = all_table[table_num].col_num;all_table[table_num].column[c] = col_name[col];all_table[table_num].col_num++; col++;//移動至下一個列名的第一位i = i + k + 1;k = 0;}else if (ins[i + k] == ')' || ins[i + k] == '）'){//把每列的名字給到對應表格的column數組中，對應列數+1int 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;}}//解析指令獲取文件名，記錄到總表格數組中i += 4; //移動到指令中file的第一位string filename;while (ins[i] != '\0'){filename += ins[i];i++;}all_table[table_num].file_name = filename;//創建表格文件并寫入表頭write_table(table_num, filename);//修改數據庫狀態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(); //更新數據庫狀態文件table_num++; //最后，表格數量加一//展示最新創建的表頭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;}//第二類創建語句（相當于打印已有表格）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){//找到了對應的表格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"){//給無名氏表格命名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) //沒找到{cout << "Not found TABLE " << tablename << " !" << endl;return;}}else{cout << "Error instruction!" << endl;} }//根據指令刪除表格 void Drop_table(char ins[]) {//先讀取數據庫狀態文件和現有表格列表read_my_sql();read_all_table();//解析指令獲取待刪除表名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){//找到待刪的表格，則進行數據遷移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) //沒找到{cout << "Not found TABLE " << tablename << " !" << endl;return;}write_my_sql(); //更新數據庫狀態文件read_all_table(); //修改當前表格列表 }//查看所有表格 void Table_list() {//先讀取數據庫狀態文件和現有表格列表read_my_sql();read_all_table();//依次讀取每張表格的數據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;}} }//向表格中插入數據 void Insert_table_data(char ins[]) {//先讀取數據庫狀態文件和現有表格列表read_my_sql();read_all_table();//解析指令獲取表名string tablename;int i = 12; //移動到指令中name的第一位while (ins[i] != ' '){tablename += ins[i];i++;}all_table[table_num].table_name = tablename;//根據表名打開對應文件，讀取表格數據int index;string filename;bool flag = 1;for (int j = 0; j < my_sql_num; j++){if (my_sql[j].table_name == tablename){//找到了對應的表格index = my_sql[j].index;filename = my_sql[j].file_name;read_table_data(index, filename);flag = 0;break;}}if (flag == 1) //沒找到{cout << "Not found TABLE " << tablename << " !" << endl;return;}i += 1; //第一類插入語句if (ins[i] == 'V') {i += 8; //i移動到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] == '，'){//把每列的值給到對應表格的值數組中，對應列數+1table_data[row][col] = col_value[num];num++; col++;//移動至下一個值i = i + k + 1;k = 0;}else if (ins[i + k] == ')' || ins[i + k] == '）'){//把每列的值給到對應表格的值數組中，對應列數+1table_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);}//第二類插入語句else if (ins[i] == '(') {//獲取給定列名稱和添加的值i += 1; //i移動到column[i]的第一位int k = 0;string cols[50]; //暫存column[i]的值int num = 0; //給定值的個數while (true){cols[num] += ins[i + k];k++;if (ins[i + k] == ',' || ins[i + k] == '，'){num++;//移動至下一個值i = i + k + 1;k = 0;}else if (ins[i + k] == ')' || ins[i + k] == '）'){num++;i = i + k + 1;break;}}i += 9; //i移動到value[i]的第一位k = 0;string value[50]; //暫存value[i]的值num = 0; //給定值的個數while (true){string col_value;value[num] += ins[i + k];k++;if (ins[i + k] == ',' || ins[i + k] == '，'){num++;//移動至下一個值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; //表示是否為缺省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"; //缺省值默認為空}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;} }//刪除表格數據 void Delete_table_data(char ins[]) {//先讀取數據庫狀態文件和現有表格列表read_my_sql();read_all_table();//第一類刪除語句if (ins[7] == 'F'){//解析指令獲取表名string tablename;int i = 12; //移動到指令中name的第一位while (ins[i] != ' '){tablename += ins[i];i++;}all_table[table_num].table_name = tablename;//讀取表格數據 int index;string filename;bool flag = 1; for (int j = 0; j < my_sql_num; j++){if (my_sql[j].table_name == tablename){//找到了對應的表格index = my_sql[j].index;filename = my_sql[j].file_name;read_table_data(index, filename);flag = 0;break;}}if (flag == 1) //沒找到{cout << "Not found TABLE " << tablename << " !" << endl;return;}i += 7; //i移動到待刪除的column第一位string column;while (ins[i] != ' '){column += ins[i];i++;}i += 3; //i移動到待刪除的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;//先找到刪除的列的下標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;//再逐行搜索滿足條件的記錄for (int k = 0; k < row; k++){if (table_data[k][column_index] == value){tag = 0;//找到待刪行，進行數據遷移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);}}//第二類刪除語句else if (ins[7] == '*' && ins[9]=='F'){//解析指令獲取表名string tablename;int i = 14; //移動到指令中name的第一位while (ins[i] != '\0'){tablename += ins[i];i++;}all_table[table_num].table_name = tablename;//讀取表格數據 int index;string filename;bool flag = 1;for (int j = 0; j < my_sql_num; j++){if (my_sql[j].table_name == tablename){//找到了對應的表格index = my_sql[j].index;filename = my_sql[j].file_name;read_table_data(index, filename);flag = 0;break;}}if (flag == 1) //沒找到{cout << "Not found TABLE " << tablename << " !" << endl;return;}all_table[index].row_num = 0; //刪除所有行cout << "DELETE SUCCESS !" << endl;printf_table(index);//修改表格文件write_table_data(index, filename);}else{cout << "Error instruction!" << endl;} }//修改表格數據 void Updata_table_data(char ins[]) {//先讀取數據庫狀態文件和現有表格列表read_my_sql();read_all_table();//解析指令獲取表名string tablename;int i = 7; //移動到指令中name的第一位while (ins[i] != ' '){tablename += ins[i];i++;}all_table[table_num].table_name = tablename;//根據表名打開對應文件，讀取表格數據int index;string filename;bool flag = 1;for (int j = 0; j < my_sql_num; j++){if (my_sql[j].table_name == tablename){//找到了對應的表格index = my_sql[j].index;filename = my_sql[j].file_name;read_table_data(index, filename);flag = 0;break;}}if (flag == 1) //沒找到{cout << "Not found TABLE " << tablename << " !" << endl;return;}i += 5; //移動到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; //第一類更新語句num++;break;}else if (ins[i + k] == 'W'){tag = 2; //第二類更新語句num++;//最后一句多了一個空格，刪去之string temp = s[num - 1].substr(0, s[num - 1].size() - 1);s[num - 1] = temp;i = i + k + 6; //i 移動到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){//對表格每一列進行遍歷，搜索column[]數組判斷是否需要更改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]) {//更改這一列每一行的值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是對應要修改的值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){//記錄限制條件 column = valuestring clmn, val;while (ins[i] != ' '){clmn += ins[i];i++;}i += 3;while (ins[i] != '\0'){val += ins[i];i++;}//找到對應的列的下標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;}//對表格每一列進行遍歷，搜索column[]數組判斷是否需要更改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]){//只更改這一列滿足限制條件的行的值for (int m = 0; m < all_table[index].row_num; m++){//判斷是否滿足條件if (table_data[m][column_index] == val){//m是表格的某一行，j是表格的某一列，n是對應要修改的值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;} }//選擇表格數據并展示 void Selete_table_data(char ins[]) {//先讀取數據庫狀態文件和現有表格列表read_my_sql();read_all_table();if (ins[7] == '*'){//解析指令獲取表名string tablename;int i = 14; //移動到指令中name的第一位while (ins[i] != '\0' && ins[i] != ' '){tablename += ins[i];i++;}//根據表名打開對應文件，讀取表格數據int index;string filename;bool flag = 1;for (int j = 0; j < my_sql_num; j++){if (my_sql[j].table_name == tablename){//找到了對應的表格index = my_sql[j].index;filename = my_sql[j].file_name;read_table_data(index, filename);flag = 0;break;}}if (flag == 1) //沒找到{cout << "Not found TABLE " << tablename << " !" << endl;return;}//從TABLE name里選擇所有列展示，即展示整個TABLEif (ins[i] == '\0'){printf_table(index);}//對返回的查詢結果按某些列進行排序展示else if (ins[i] == ' ' && ins[i + 1] == 'O'){i += 10; //移動到 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 移動到ASC|DESC首位break;}}//找到對應的列的下標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]){//交換兩行元素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]){//交換兩行元素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//打印表頭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;//打印數據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 移動到column第一位//記錄限制條件 column = valuestring clmn, val;while (ins[i] != ' '){clmn += ins[i];i++;}i += 1;// column = valueif (ins[i] == '='){i += 2;while (ins[i] != '\0' && ins[i] != ' '){val += ins[i];i++;}//找到對應的列的下標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//打印表頭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;//打印數據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; //移動到新表格文件名第一位string new_filename;while (ins[i] != '\0'){new_filename += ins[i];i++;}//打印//打印表頭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;//打印數據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;}}//創建新表寫入文件ofstream out_file(new_filename, ios::out);//寫入表頭for (int j = 0; j < all_table[index].col_num; j++){out_file << all_table[index].column[j] << " ";}out_file << endl;//寫入數據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();//修改數據庫狀態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(); //更新數據庫狀態文件}}// column > valueelse if (ins[i] == '>'){i += 2;while (ins[i] != '\0'){val += ins[i];i++;}//找到對應的列的下標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//打印表頭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;//打印數據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(學號)else if (ins[i] == '<'){i += 2;//找到對應的列的下標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;}//找學號最大值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//打印表頭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;//打印數據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; //移動到 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 移動到name首位break;}}//解析表名string tablename;while (ins[i] != '\0' && ins[i] != ' '){tablename += ins[i];i++;}//根據表名打開對應文件，讀取表格數據int index;string filename;bool tag = 1;for (int j = 0; j < my_sql_num; j++){if (my_sql[j].table_name == tablename){//找到了對應的表格index = my_sql[j].index;filename = my_sql[j].file_name;read_table_data(index, filename);tag = 0;break;}}if (tag == 1) //沒找到{cout << "Not found TABLE " << tablename << " !" << endl;return;}bool flag[50]; //給每一列做標記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;}}}//打印表頭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;//打印數據for (int m = 0; m < all_table[index].row_num; m++){bool print = 1; //判斷要不要打印 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++;}//解析指令獲取表名i += 7;string tablename;while (ins[i] != '\0'){tablename += ins[i];i++;}//根據表名打開對應文件，讀取表格數據int index;string filename;bool flag = 1;for (int j = 0; j < my_sql_num; j++){if (my_sql[j].table_name == tablename){//找到了對應的表格index = my_sql[j].index;filename = my_sql[j].file_name;read_table_data(index, filename);flag = 0;break;}}if (flag == 1) //沒找到{cout << "Not found TABLE " << tablename << " !" << endl;return;}//找到對應的列的下標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//打印表頭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;//打印數據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; //移動到 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 移動到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;//根據表名打開對應文件，讀取表格數據int index;string filename;bool tag = 1;for (int j = 0; j < my_sql_num; j++){if (my_sql[j].table_name == tablename){//找到了對應的表格index = my_sql[j].index;filename = my_sql[j].file_name;read_table_data(index, filename);tag = 0;break;}}if (tag == 1) //沒找到{cout << "Not found TABLE " << tablename << " !" << endl;return;}bool flag[50]; //給每一列做標記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;}}}//從TABLE name里選擇若干列展示if (ins[i] == '\0'){//打印表頭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;//打印數據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;}}//從TABLE name里選擇若干列展示else if (ins[i] == ' ' && ins[i + 1] == 'W'){i += 7; //移動到column首位//記錄限制條件 column = valuestring clmn, val;while (ins[i] != ' '){clmn += ins[i];i++;}i += 3;while (ins[i] != '\0'){val += ins[i];i++;}//找到對應的列的下標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;}//打印表頭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;//打印數據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; }//判斷是否為空行（即m是否為字母） bool is_not_endl(char m) {if (((m >= 'a') && (m <= 'z')) || ((m >= 'A') && (m <= 'Z')))return true;return false; }

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