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prajwal3114prajwal3114
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Merge pull request #35 from Shreyanshi210205/database
feat: add database file with student records
2 parents 160b36d + 1e26396 commit 236c33a

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‎Src/Mini_Database_Engine/database.cpp‎

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#include <iostream>
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#include <fstream>
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#include <string>
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#include <vector>
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#include <unordered_map>
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#include <limits>
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#include <algorithm>
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using namespace std;
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class Record {
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public:
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vector<string> values;
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Record(const vector<string>& vals) : values(vals) {}
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void display() const{
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for (size_t i = 0; i < values.size(); i++)
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cout << values[i] << "\t";
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cout << endl;
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}
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};
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class Table {
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private:
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string name;
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vector<string>columns;
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vector<Record>records;
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public:
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Table() {
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}
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Table(const string& tableName, const vector<string>& cols) : name(tableName), columns(cols) {
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}
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const string& getName() const { return name; }
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const vector<string>& getColumns() const { return columns;
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}
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void insertRecord(const vector<string>& values) {
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if (values.size() != columns.size()) {
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cerr << "Error: Column count mismatch!" << endl;
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return;
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}
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records.emplace_back(values);
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cout << "Record inserted successfully.\n";
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}
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void displayAll() const {
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cout << "\nTable: " << name << endl;
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for (size_t i = 0; i < columns.size(); i++)
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cout << columns[i] << "\t";
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cout << "\n--------------------------\n";
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for (size_t i = 0; i < records.size(); i++)
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records[i].display();
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}
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void deleteRecord(int index) {
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if (index < 0 || index >= (int)records.size()) {
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cerr << "Error: Invalid record index." << endl;
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return;
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}
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records.erase(records.begin() + index);
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cout << "Record deleted successfully.\n";
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}
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void updateRecord(int index, const vector<string>& newValues) {
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if (index < 0 || index >= (int)records.size()) {
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cerr << "Error: Invalid record index." << endl;
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return;
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}
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if (newValues.size() != columns.size()) {
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cerr << "Error: Column count mismatch!" << endl;
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return;
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}
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records[index] = Record(newValues);
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cout << "Record updated successfully.\n";
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}
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void query(const string& column, const string& value) const {
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int colIndex = -1;
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for (size_t i = 0; i < columns.size(); i++) {
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if (columns[i]==column) { colIndex = i; break; }
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}
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if (colIndex == -1) { cerr << "Error: Column not found!" << endl; return; }
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cout << "\nQuery Results for "<< column<< " = " << value << ":\n";
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for (size_t i = 0; i < records.size(); i++) {
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if (records[i].values[colIndex] == value)
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records[i].display();
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}
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}
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void saveToFile(ofstream& out) const {
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out << name << "\n" << columns.size() << "\n";
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for (size_t i = 0; i < columns.size(); i++) out << columns[i] << "\n";
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out << records.size() << "\n";
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for (size_t i = 0; i < records.size(); i++) {
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for (size_t j = 0; j < records[i].values.size(); j++)
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out << records[i].values[j] << "\n";
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}
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}
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void loadFromFile(ifstream& in) {
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size_t colCount, recCount;
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in >> colCount;
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in.ignore(numeric_limits<streamsize>::max(),'\n');
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columns.clear();
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for (size_t i = 0; i < colCount; i++) {
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string col;
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getline(in, col);
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columns.push_back(col);
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}
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in >> recCount;
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in.ignore(numeric_limits<streamsize>::max(),'\n');
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records.clear();
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for (size_t i = 0; i < recCount; i++) {
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vector<string> vals;
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for (size_t j = 0; j < colCount; j++) {
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string val;
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getline(in, val);
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vals.push_back(val);
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}
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records.emplace_back(vals);
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}
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}
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};
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class Database {
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private:
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unordered_map<string, Table> tables;
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public:
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void createTable(const string& name, const vector<string>& columns) {
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if (tables.find(name) != tables.end()) { cerr << "Error: Table already exists!" << endl; return; }
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tables[name] = Table(name, columns);
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cout << "Table '" << name << "' created successfully.\n";
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}
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Table* getTable(const string& name) {
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auto it = tables.find(name);
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if (it == tables.end()) { cerr << "Error: Table not found!" << endl; return nullptr; }
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return &(it->second);
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}
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void saveDatabase(const string& filename)const {
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ofstream out(filename.c_str());
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if (!out) { cerr << "Error: Cannot open file for saving.\n"; return; }
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out << tables.size() << "\n";
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for (auto it = tables.begin(); it != tables.end(); ++it)
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it->second.saveToFile(out);
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cout << "Database saved to " << filename << endl;
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}
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void loadDatabase(const string& filename) {
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ifstream in(filename.c_str());
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if (!in) { cerr << "No previous database found. Starting fresh.\n"; return; }
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size_t tableCount;
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in >> tableCount; in.ignore(numeric_limits<streamsize>::max(), '\n');
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tables.clear();
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for (size_t i = 0; i < tableCount; i++) {
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string tableName;
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getline(in, tableName);
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Table t;
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t.loadFromFile(in);
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tables[tableName] = t;
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}
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cout << "Database loaded from " << filename << endl;
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}
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};
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int main() {
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Database db;
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db.loadDatabase("database.txt");
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int choice;
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while (true) {
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cout << "\n----- Mini Database Engine -----\n";
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cout << "1. Create Table\n2. Insert Record\n3. Display Table\n4. Delete Record\n";
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cout << "5. Update Record\n6. Query Data\n7. Save & Exit\nEnter choice: ";
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cin >> choice;
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cin.ignore(numeric_limits<streamsize>::max(), '\n');
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if (choice == 1) {
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string name;
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int cols;
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cout << "Enter table name: ";
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getline(cin, name);
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cout << "Enter number of columns: ";
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cin >> cols;
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cin.ignore(numeric_limits<streamsize>::max(), '\n');
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vector<string> columns(cols);
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cout << "Enter column names (one per line):\n";
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for (int i = 0; i < cols; i++)
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getline(cin, columns[i]);
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db.createTable(name, columns);
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}
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else if (choice == 2) {
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string tname;
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cout << "Enter table name: ";
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getline(cin, tname);
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Table* t = db.getTable(tname);
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if (t) {
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vector<string> vals;
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for (size_t i = 0; i < t->getColumns().size(); i++) {
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string val;
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cout << t->getColumns()[i] << ": ";
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getline(cin, val);
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vals.push_back(val);
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}
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t->insertRecord(vals);
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}
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}
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else if (choice == 3) {
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string tname;
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cout << "Enter table name: ";
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getline(cin, tname);
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Table* t = db.getTable(tname);
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if (t) t->displayAll();
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}
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else if (choice == 4) {
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string tname;
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int index;
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cout<< "Enter table name: ";
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getline(cin, tname);
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cout<< "Enter record index (starting from 0): ";
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cin>> index;
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cin.ignore(numeric_limits<streamsize>::max(), '\n');
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Table* t = db.getTable(tname);
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if (t) t->deleteRecord(index);
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}
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else if (choice == 5) {
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string tname;
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int index;
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cout << "Enter table name: ";
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getline(cin, tname);
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Table* t = db.getTable(tname);
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if (t) {
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cout<< "Enter record index: ";
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cin>> index;
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cin.ignore(numeric_limits<streamsize>::max(), '\n');
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vector<string> newVals;
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for (size_t i = 0; i < t->getColumns().size(); i++) {
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string val;
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cout<< t->getColumns()[i] << ": ";
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getline(cin, val);
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newVals.push_back(val);
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}
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t->updateRecord(index, newVals);
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}
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}
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else if (choice == 6) {
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string tname, col, val;
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cout<< "Enter table name: ";
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getline(cin, tname);
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cout<< "Enter column to search: ";
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getline(cin, col);
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cout<< "Enter value: ";
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getline(cin, val);
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Table* t = db.getTable(tname);
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if (t) t->query(col, val);
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}
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else if (choice == 7) {
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db.saveDatabase("database.txt");
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cout << "Exiting...\n";
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break;
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}
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else cout << "Invalid choice. Try again.\n";
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}
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return 0;
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}
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#ifdef _WIN32
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#include <windows.h>
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int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
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return main();
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}
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#endif

‎Src/Mini_Database_Engine/output/database.exe‎

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‎Src/Mini_Database_Engine/output/database.txt‎

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2
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ss
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2
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s
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s
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0
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Student
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2
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Name
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Class
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1
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Shreya
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2

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