C++ RELATIONAL DATABASE OPERATIONS (SELECT, PROJECT, JOIN)

/* Homemade relational database. Implements Select, Project, Join and Union operations. Dan Ross Orginal Mar 2013 Updated Mar 2017 */ #include  #include  #include  #include  #pragma warning( disable : 4267) #pragma warning( disable : 4996) using namespace std; // **** THE TABLES **** // Use 800kB global tables cuz RAM is cheap and labor is not! // Seriously, a more efficient memory implementation would // use pointers and dynamic memory (using new and/or malloc) // but that often requires tricky pointer arithmetic char T1[100][100][80]; char T2[100][100][80]; /* Prints out a table ******* HINTS!! ******* Does anybody read this stuff???! See this function right here? It has a basic table looping structure that you may find helpful in building the other functions you need. Just squeeze in some logic here and there with maybe strcmp and strcpy. */ void printTable(char T[100][100][80]) { int i = 0, j = 0; while (T[i][j][0]) { // look for null char at T[i][j][0] while (T[i][j][0]){ cout << left << setw(20) << T[i][j];// string at T[i][j] j++; } cout << endl; i++; j = 0; } cout << endl; } /* Erases a table */ void eraseTable(char T[100][100][80]) { // erase the destination array for (int i = 0; i < 100; i++) // rows for (int j = 0; j < 100; j++) // cols for (int k = 0; k < 80; k++) // chars T[i][j][k] = 0; } void eraseArray(int A[], int size) { for (int i = 0; i < size; i++) A[i] = 0; } /* Reads a file into a table */ void filltable(char filename[80], char Table[100][100][80]) { // open source file ifstream fin(filename); if (!fin) { cerr << "Input file could not be opened "; exit(1); } char line[80]; char buf[80]; // table rows and cols int row = 0; int col = 0; // Copy file into table fin.getline(line, 80); while (line[0]){ col = 0; // reset col //cout << line << endl << endl; // parse this line int i = 0; int j = 0; int len = strlen(line); for (i = 0; i <= len; i++){ if ((line[i] == ',') || (line[i] == 0)){ // delimiters strncpy(buf, line + j, i - j); buf[i - j] = 0; // null terminator j = i + 1; // scoot up j // copy buffer to table array strcpy(Table[row][col], buf); col++; //cout << "Hey: " << buf << endl; } } // get another line fin.getline(line, 80); row++; } } /* Performs a select operation on a table. Receives a table. Returns a table consisting of only the rows which have the specified 'value' in the specified 'col' */ void select(char Tout[100][100][80], char Tin[100][100][80], int col, char * value) { // erase the destination array eraseTable(Tout); // YOU WRITE THIS } /* Performs a project operation on a table. Receives a table. Returns a table consisting of the specified cols. The 'cols' parameter is a set of boolean flags where true means we want this row in the resulting table */ void project(char Tout[100][100][80], char Tin[100][100][80], int cols[100]) { // erase the destination array eraseTable(Tout); // YOU WRITE THIS } /* Performs a join operation on a table. Receives 2 tables and joins them. Returns only the rows where the value in table1's T1col matches the value in table2's T2col */ void join(char Tout[100][100][80], char T1[100][100][80], char T2[100][100][80], int T1col, int T2col) { // erase the destination array eraseTable(Tout); // YOU WRITE THIS } /* Makes a 3rd table containing all the stuff in 2 other tables. The 2 input tables must have the same schema. */ void Union(char Tout[100][100][80], char T1[100][100][80], char T2[100][100][80]) { // erase the destination array eraseTable(Tout); // YOU WRITE THIS } /* Reads in some tables and does operations on them */ void main(void) { filltable("Professors.txt", T1); filltable("Students.txt", T2); cout << "Original Professors table: "; printTable(T1); cout << "Original Students table: "; printTable(T2); // select // locals are created in the stack (except statics) // so use a static to prevent stack overflow static char Temp1[100][100][80]; select(Temp1, T2, 1, "555 Riley"); cout << " SELECT TEST: Temp1 = Students[Address = 555 Riley] "; printTable(Temp1); // project cout << " PROJECT TEST: Temp2 = Students[Name, Phone] "; static char Temp2[100][100][80]; // dynamic arrays are also easy on the stack // cuz they point to the heap int * cols = new int[100]; eraseArray(cols, 100); cols[0] = cols[2] = 1; project(Temp2, T2, cols); printTable(Temp2); // join cout << " JOIN TEST: Temp3 = Students[address = address]Professors "; static char Temp3[100][100][80]; join(Temp3, T1, T2, 1, 1); printTable(Temp3); // union cout << " UNION TEST: Temp4 = Students UNION MoreStudents "; static char T3[100][100][80]; filltable("MoreStudents.txt", T3); static char Temp4[100][100][80]; Union(Temp4, T2, T3); printTable(Temp4); }