HW 3(Database) is done.

homework_3/database.h

+#ifndef DATABASE_H
+#define DATABASE_H
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <libpq-fe.h>
+
+void checkConnectionError(PGconn *conn);
+void checkInqueryError(PGresult *res);
+
+void checkConnectionError(PGconn *conn)
+{
+  if (PQstatus(conn) == CONNECTION_BAD)
+    {
+        printf("We're unable to connect to the database\n");
+        PQfinish(conn);
+        exit(-1);
+    }
+
+  return;
+}
+
+void checkInqueryError(PGresult *res)
+{
+  if (PQresultStatus(res) != PGRES_TUPLES_OK)
+  {
+    printf("We did not get any data!\n");
+    PQclear(res);
+    exit(-1);
+  }
+  return;
+}
+
+void dispResult(PGresult *res)
+{
+  int numTuple = PQntuples(res);
+  int numField = PQnfields(res);
+
+  int i,j;
+
+  printf("%5s\t", "No.");
+  for (i = 0; i < numField; i++)
+  {
+    printf("%15s\t", PQfname(res,i));
+  }
+  printf("\n");
+
+  for (j = 0; j < numTuple; j++)
+  {
+    printf("%5d\t", j+1);
+    for (i = 0; i < numField; i++)
+    {
+      printf("%15s\t", PQgetvalue(res,j,i));
+    }
+    printf("\n");
+  }
+
+  return;
+}
+
+#endif

homework_3/dev_version/database.h

+#ifndef DATABASE_H
+#define DATABASE_H
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <libpq-fe.h>
+
+void checkConnectionError(PGconn *conn);
+void checkUnvoidInqueryError(PGresult *res);
+void checkVoidInqueryError(PGresult *res);
+void dispTable(PGresult *res);
+
+void checkConnectionError(PGconn *conn)
+{
+  if (PQstatus(conn) == CONNECTION_BAD)
+    {
+        printf("We're unable to connect to the database\n");
+        PQfinish(conn);
+        exit(-1);
+    }
+
+  return;
+}
+
+void checkUnvoidInqueryError(PGresult *res)
+{
+  if (PQresultStatus(res) != PGRES_TUPLES_OK)
+  {
+    printf("We did not get any data!\n");
+    PQclear(res);
+    exit(-1);
+  }
+  return;
+}
+
+void checkVoidInqueryError(PGresult *res)
+{
+  if (PQresultStatus(res) != PGRES_COMMAND_OK)
+  {
+    printf("SQL command failed.\n");
+    PQclear(res);
+    exit(-1);
+  }
+  return;
+}
+
+void dispTable(PGresult *res)
+{
+  int numTuple = PQntuples(res);
+  int numField = PQnfields(res);
+
+  int i,j;
+
+  printf("%5s\t", "No.");
+  for (i = 0; i < numField; i++)
+  {
+    printf("%15s\t", PQfname(res,i));
+  }
+  printf("\n");
+
+  for (j = 0; j < numTuple; j++)
+  {
+    printf("%5d\t", j+1);
+    for (i = 0; i < numField; i++)
+    {
+      printf("%15s\t", PQgetvalue(res,j,i));
+    }
+    printf("\n");
+  }
+
+  return;
+}
+
+#endif

homework_3/dev_version/functions.h

+#ifndef FUNCTIONS_H
+#define FUNCTIONS_H
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "database.h"
+#include "ui.h"
+
+typedef struct student {
+  int student_code;
+  char first_name[34];
+  char last_name[34];
+  char birthdate[11];
+  double average_grade;
+} student_t;
+
+typedef struct subject {
+  int id_subject;
+  int credits;
+  char subject_code[12];
+  char name[256];
+  char teacher[64];
+} subject_t;
+
+typedef struct grade {
+  int id_grade;
+  int id_subject;
+  int student_code;
+  int grade;
+} grade_t;
+
+
+void insertStudentRecord(PGconn *conn);
+student_t inputStudentData(void);
+int genUniqueStudentCode(PGconn *conn);
+void modifyStudentRecord(PGconn *conn);
+char *getIdtoEdit(PGconn *conn, const char filedName[], const char database[]);
+void deleteStudentRecord(PGconn *conn);
+
+
+void insertSubjectRecord(PGconn *conn);
+subject_t inputSubjectData(void);
+void modifySubjectRecord(PGconn *conn);
+char *subjectChoice(PGconn *conn);
+void deleteSubjectRecord(PGconn *conn);
+
+void GradeRecord(PGconn *conn);
+
+void dispStudentTableByGrade(PGconn *conn);
+
+
+
+void insertStudentRecord(PGconn *conn)
+{
+  PGresult *res;
+  char query[128];
+
+  student_t addedData = inputStudentData();
+
+  addedData.student_code = genUniqueStudentCode(conn);
+
+  sprintf(query, "insert into student values ('%d','%s','%s','%s','%lf')", addedData.student_code, addedData.first_name, addedData.last_name, addedData.birthdate, 0.00);
+
+
+  res = PQexec(conn, query);
+  checkVoidInqueryError(res);
+
+  PQclear(res);
+
+  return;
+}
+
+student_t inputStudentData(void)
+{
+  student_t data;
+
+  printf("Please insert student's first name.\n>>");
+  scanf("%s",data.first_name);
+
+  printf("Please insert student's last name.\n>>");
+  scanf("%s",data.last_name);
+
+  sprintf(data.birthdate, "%04d-%02d-%02d", getInt(1900,2100,"Please insert student's birth year.\n"),
+                            getInt(1,12,"Please insert student's birth month in digit\n"),
+                            getInt(1,31,"Please insert student's birth day.\n"));
+
+  return data;
+}
+
+int genUniqueStudentCode(PGconn *conn)
+{
+  int generatedStudentCode;
+  PGresult *res;
+
+  res = PQexec(conn, "select max(student_code) from student");
+  checkUnvoidInqueryError(res);
+
+  generatedStudentCode = atoi(PQgetvalue(res, 0, 0));
+
+  PQclear(res);
+
+  return generatedStudentCode+1;
+}
+
+void modifyStudentRecord(PGconn *conn)
+{
+  char *studentCode;
+  PGresult *res;
+  char query[128];
+  student_t modifiedData;
+
+  studentCode = getIdtoEdit(conn, "first_name", "student");
+
+  if (studentCode != NULL)
+  {
+    printf("Modifying student %s.\n", studentCode);
+    modifiedData = inputStudentData();
+
+    sprintf(query, "update student set first_name = '%s', last_name = '%s', birthdate = '%s' where student_code = '%s'", modifiedData.first_name, modifiedData.last_name, modifiedData.birthdate, studentCode);
+
+    res = PQexec(conn, query);
+    checkVoidInqueryError(res);
+
+    PQclear(res);
+  }
+
+  return;
+}
+
+char *getIdtoEdit(PGconn *conn, const char fieldName[], const char database[])
+{
+  char *id;
+  PGresult *res;
+  char query[128];
+  char fieldData[32];
+  int numChosen;
+
+  printf("Please insert %s.\n>>", fieldName);
+  scanf("%s", fieldData);
+
+  sprintf(query, "select * from %s where %s = '%s'", database, fieldName, fieldData);
+
+  res = PQexec(conn, query);
+  checkUnvoidInqueryError(res);
+
+  printf("Chooes the one to edit or exit with 0.\n");
+  dispTable(res);
+
+  numChosen = getInt(0,PQntuples(res),"");
+
+  id = PQgetvalue(res, numChosen-1, 0);
+
+  PQclear(res);
+
+  return id;
+}
+
+void deleteStudentRecord(PGconn *conn)
+{
+  char *studentCode;
+  PGresult *res;
+  char query[128];
+  student_t modifiedData;
+
+  studentCode = getIdtoEdit(conn, "first_name", "student");
+
+  printf("Student %s was deleted.\n", studentCode);
+
+  sprintf(query, "delete from student where student_code = '%s'", studentCode);
+
+  res = PQexec(conn, query);
+  checkVoidInqueryError(res);
+
+  PQclear(res);
+
+  return;
+}
+
+void insertSubjectRecord(PGconn *conn)
+{
+  PGresult *res;
+  char query[128];
+
+  subject_t addedSubject = inputSubjectData();
+
+  sprintf(query, "insert into subject (credits, subject_code, name, teacher) values ('%d','%s','%s','%s')", addedSubject.credits, addedSubject.subject_code, addedSubject.name, addedSubject.teacher);
+
+
+  res = PQexec(conn, query);
+  checkVoidInqueryError(res);
+
+  PQclear(res);
+
+  return;
+}
+
+subject_t inputSubjectData(void)
+{
+  subject_t data;
+
+  printf("Please insert subject's name.\n>>");
+  scanf("%s",data.name);
+
+  data.credits = getInt(1,30,"Please insert subject's credit point.\n");
+
+  printf("Please insert subject's code.(ie. AAA0000)\n>>");
+  scanf("%s",data.subject_code);
+
+  printf("Please insert teacher's name.\n>>");
+  scanf("%s",data.teacher);
+
+  return data;
+}
+
+void modifySubjectRecord(PGconn *conn)
+{
+  char *subjectId;
+  PGresult *res;
+  char query[128];
+  subject_t modifiedData;
+
+  subjectId = subjectChoice(conn);
+
+  printf("Modifying subject record %s.\n", subjectId);
+  modifiedData = inputSubjectData();
+
+  sprintf(query, "update subject set credits = '%d', subject_code = '%s', name = '%s', teacher = '%s' where id_subject = '%s'", modifiedData.credits, modifiedData.subject_code, modifiedData.name, modifiedData.teacher, subjectId);
+
+  res = PQexec(conn, query);
+  checkVoidInqueryError(res);
+
+  PQclear(res);
+
+  return;
+}
+
+char *subjectChoice(PGconn *conn)
+{
+  char *id;
+  PGresult *res;
+  char query[128];
+  int numChosen;
+
+
+  sprintf(query, "select * from subject");
+
+  res = PQexec(conn, query);
+  checkUnvoidInqueryError(res);
+
+  printf("Chooes the a subject.\n");
+  dispTable(res);
+
+  numChosen = getInt(1,PQntuples(res),"");
+
+  id = PQgetvalue(res, numChosen-1, 0);
+
+  PQclear(res);
+
+  return id;
+}
+
+void deleteSubjectRecord(PGconn *conn)
+{
+  char *subjectId;
+  PGresult *res;
+  char query[128];
+  subject_t modifiedData;
+
+  subjectId = subjectChoice(conn);
+
+  printf("Deleting subject record %s.\n", subjectId);
+
+  sprintf(query, "delete from subject where id_subject = '%s'", subjectId);
+
+  res = PQexec(conn, query);
+  checkVoidInqueryError(res);
+
+  PQclear(res);
+
+  return;
+}
+
+
+
+void GradeRecord(PGconn *conn)
+{
+  char *subjectId;
+  char *studentCode;
+  char mess[128];
+  int newGrade;
+  PGresult *res;
+  char query[128];
+
+  subjectId = subjectChoice(conn);
+  studentCode = getIdtoEdit(conn, "first_name", "student");
+
+  sprintf(mess, "Please insert new grade for student %s in subject %s\n", studentCode, subjectId);
+  newGrade = getInt(0, 5, mess);
+
+  sprintf(query, "select * from grade where id_subject = '%s' and student_code = '%s'", subjectId,studentCode);
+  res = PQexec(conn, query);
+  checkUnvoidInqueryError(res);
+
+  if (PQgetisnull(res,0,0) == 1)
+  {
+    sprintf(query, "insert into grade (id_subject, student_code, grade) values ('%s', '%s', '%d')", subjectId, studentCode, newGrade);
+    res = PQexec(conn, query);
+    checkVoidInqueryError(res);
+    printf("Grade data was inserted.\n");
+  }
+  else
+  {
+    sprintf(query, "update grade set grade = '%d' where id_subject = '%s' and student_code = '%s'", newGrade, subjectId, studentCode);
+    res = PQexec(conn, query);
+    checkVoidInqueryError(res);
+    printf("Grade data was updated.\n");
+  }
+
+  sprintf(query, "select cast(sum(grade*credits) as float)/sum(credits) from grade join subject on student_code=student_code where student_code = '%s'", studentCode);
+  res = PQexec(conn, query);
+  checkUnvoidInqueryError(res);
+;
+
+  sprintf(query, "update student set average_grade = '%s' where student_code = '%s'", PQgetvalue(res,0,0), studentCode);
+  res = PQexec(conn, query);
+  checkVoidInqueryError(res);
+
+  PQclear(res);
+
+  return;
+}
+
+void dispStudentTableByGrade(PGconn *conn)
+{
+  PGresult *res;
+  char query[128];
+
+  double lowLimit = getDouble(0, 5, "Please input lower limit of grade.\n");
+  double upLimit = getDouble(lowLimit, 5, "Please input upper limit of grade.\n");
+
+  sprintf(query, "select * from student where average_grade >= %lf and average_grade <= %lf order by average_grade desc", lowLimit, upLimit);
+
+
+  res = PQexec(conn, query);
+  checkUnvoidInqueryError(res);
+
+  dispTable(res);
+
+  PQclear(res);
+
+  return;
+}
+
+
+#endif

homework_3/dev_version/main.c

+//gcc main.c -L/Library/PostgreSQL/9.6/lib  -I/Library/PostgreSQL/9.6/include -lpq
+
+#include <stdio.h>
+#include "functions.h"
+#include "database.h"
+#include "ui.h"
+
+#define LOGIN_INFO "dbname=mveb165842 host=ewis.pld.ttu.ee port=5432 user=mveb165842 password=7ez6d0mu"
+
+#define WELCOME_MES "Welcome. This program accesses database mveb165842 at ewis.pld.ttu.ee.\n"
+#define MAIN_MENU "Main menu\n1: Edit student record\n2: Edit subject record\n3: Edit grade record\n4: Display students table \n5: Exit\n"
+#define EDIT_MENU "1: Insert\n2: Modify\n3: Delete\n"
+#define YES_NO "1: Yes\n2: No\n"
+
+int editStudentRecord(PGconn *conn);
+int editSubjectRecord(PGconn *conn);
+int editGradeRecord(PGconn *conn);
+int dispStudentTable(PGconn *conn);
+int normalExit(PGconn *conn);
+
+
+int main()
+{
+    PGconn *conn;
+
+    int (*func[5])() = {editStudentRecord, editSubjectRecord, editGradeRecord, dispStudentTable, normalExit};
+
+    int exitFlag = 0;
+
+
+    checkConnectionError(conn = PQconnectdb(LOGIN_INFO));
+
+    printf(WELCOME_MES);
+
+    while ((*func[getInt(1,5,MAIN_MENU)-1])(conn) == 0);
+
+    PQfinish(conn);
+
+    return 0;
+}
+
+int editStudentRecord(PGconn *conn)
+{
+    void (*func[3])() = {insertStudentRecord, modifyStudentRecord, deleteStudentRecord};
+
+    do
+    {
+            (*func[getInt(1,3,"Editing student record\n" EDIT_MENU)-1])(conn);
+    } while(getInt(1, 2, "Edit more student record?\n" YES_NO) == 1);
+
+    return 0;
+}
+
+int editSubjectRecord(PGconn *conn)
+{
+    void (*func[3])() = {insertSubjectRecord, modifySubjectRecord, deleteSubjectRecord};
+
+    do
+    {
+            (*func[getInt(1,3,"Editing subject record\n" EDIT_MENU)-1])(conn);
+    } while(getInt(1, 2, "Edit more subject record?\n" YES_NO) == 1);
+
+    return 0;
+}
+
+int editGradeRecord(PGconn *conn)
+{
+    do
+    {
+            GradeRecord(conn);
+    } while(getInt(1, 2, "Add more grade record?\n" YES_NO) == 1);
+
+    return 0;
+}
+
+int dispStudentTable(PGconn *conn)
+{
+    do
+    {
+        dispStudentTableByGrade(conn);
+    } while(getInt(1, 2, "Display another table?\n" YES_NO) == 1);
+
+    return 0;
+}
+
+int normalExit(PGconn *conn)
+{
+    return -1;
+}

homework_3/dev_version/ui.h

+#ifndef UI_H
+#define UI_H
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "database.h"
+
+#define INV_INPUT "Invailed input was inserted.\n"
+
+double getDouble(double min, double max, const char mess[]);
+int getInt(int min, int max, const char mess[]);
+
+double getDouble(double min, double max, const char mess[])
+{
+    double num;
+
+    printf("%s", mess);
+
+    while(1)
+    {
+        printf(">>");
+        scanf("%lf", &num);
+        if (min <= num && num <= max)
+        {
+            break;
+        }
+        else
+        {
+            printf(INV_INPUT);
+        }
+    }
+
+    return num;
+}
+
+int getInt(int min, int max, const char mess[])
+{
+    int num;
+
+    printf("%s", mess);
+
+    while(1)
+    {
+        printf(">>");
+        scanf("%d", &num);
+        if (min <= num && num <= max)
+        {
+            break;
+        }
+        else
+        {
+            printf(INV_INPUT);
+        }
+    }
+
+    return num;
+}
+
+#endif

homework_3/functions.c

+#ifndef FUNCTION_H
+#define FUNCTION_H
+
+#include <stdio.h>
+#include "database.h"
+#include "ui.h"
+
+#define LOW_GRADE_LIMIT "Please input lower limit of grade.\n"
+#define UP_GRADE_LIMIT "Please input upper limit of grade.\n"
+
+#define STUDENT_EDIT_FUNC_LIST "What do you want to do?\n1: insert\n2: modify\n3: select\n"
+
+typedef struct date {
+    int day;
+    int month;
+    int year;
+} date_t;
+
+typedef struct student {
+    char first_name[32];
+    char last_name[32];
+    date_t date;
+} student_t;
+
+void editStudent(PGconn *conn);
+void insertStudentData(PGconn *conn);
+void modifyStudentData(PGconn *conn);
+void deleteStudentData(PGconn *conn);
+
+void editSubject(PGconn *conn);
+void addGrade(PGconn *conn);
+void dispStudentByGrade(PGconn *conn);
+
+void editStudent(PGconn *conn)
+{
+    void (*func[5])() = {insertStudentData, modifyStudentData, deleteStudentData};
+
+    while (1)
+    {
+        (*func[getInt(1,5,STUDENT_EDIT_FUNC_LIST)-1])(conn);
+
+        if (getInt(1,2,"Edit more data?\n1: Yes\n2: No\n") == 2)
+        {
+            break;
+        }
+    }
+    return;
+}
+
+void insertStudentData(PGconn *conn)
+{
+    char query[128];
+    student_t addedStudentRecord;
+
+    printf("Insert student's first name.\n>>");
+    scanf("%s", addedStudentRecord.first_name);
+
+    printf("Insert student's last name.\n>>");
+    scanf("%s",  addedStudentRecord.last_name);
+
+    printf("Insert student's birthdate. (i.e. YYYYMMDD)\n>>");
+    scanf("%4d%2d%2d", &addedStudentRecord.date.year, &addedStudentRecord.date.month, &addedStudentRecord.date.day);
+    //error check is needed!!
+
+    sprintf(query, "insert into student (first_name,last_name,date) values (%s,%s,%d%d%d)", addedStudentRecord.first_name, addedStudentRecord.last_name, addedStudentRecord.date.year, addedStudentRecord.date.month, addedStudentRecord.date.day);
+    
+
+
+    printf("%s\n" , query);
+
+    return;
+}
+
+void modifyStudentData(PGconn *conn)
+{
+    return;
+}
+
+void deleteStudentData(PGconn *conn)
+{
+    return;
+}
+
+void editSubject(PGconn *conn)
+{
+
+
+
+    return;
+}
+
+
+void addGrade(PGconn *conn)
+{
+
+
+    return;
+}
+
+
+void dispStudentByGrade(PGconn *conn)
+{
+    PGresult *res;
+    double lowLimit;
+    double upLimit;
+    char query[128];
+
+    while (1)
+    {
+        lowLimit = getDouble(0, 5, LOW_GRADE_LIMIT);
+        upLimit = getDouble(lowLimit, 5, UP_GRADE_LIMIT);
+
+        sprintf(query, "select * from student where average_grade > %lf and average_grade < %lf order by average_grade desc", lowLimit, upLimit);
+
+        res = PQexec(conn, query);
+        checkInqueryError(res);
+
+        dispResult(res);
+
+        if (getInt(1,2,"Add more data?\n1: Yes\n2: No\n") == 2)
+        {
+            break;
+        }
+    }
+
+    PQclear(res);
+
+    return;
+}
+
+#endif

homework_3/main.c

+//gcc main.c -L/Library/PostgreSQL/9.6/lib  -I/Library/PostgreSQL/9.6/include -lpq
+
+#include <stdio.h>
+#include "database.h"
+#include "ui.h"
+#include "functions.c"
+
+#define WELCOME_MES "Welcome. This program accesses database mveb165842 at ewis.pld.ttu.ee.\n"
+#define SERVICE_LIST "Choose a service from the list given below.\n1: Edit student data\n2: Edit subject data\n3: Add grade\n4: Display students' grades\n5: Exit\n"
+
+#define LOGIN_INFO "dbname=mveb165842 host=ewis.pld.ttu.ee port=5432 user=mveb165842 password=7ez6d0mu"
+
+void doExit(PGconn *conn);
+
+int main(void)
+{
+    PGconn *conn;
+    PGresult *res;
+
+    void (*func[5])() = {editStudent, editSubject, addGrade, dispStudentByGrade, doExit};
+
+    printf(WELCOME_MES);
+
+
+    checkConnectionError(conn = PQconnectdb(LOGIN_INFO));
+
+    while (1)
+    {
+            (*func[getInt(1,5,SERVICE_LIST)-1])(conn) < 0)
+    }
+
+    return 0;
+}
+
+
+void doExit(PGconn *conn)
+{
+    PQfinish(conn);
+    exit(1);
+    return;
+}

homework_3/ui.h

+#ifndef UI_H
+#define UI_H
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define INV_INPUT "Invailed input was inserted.\n"
+
+double getDouble(double min, double max, const char mess[]);
+int getInt(int min, int max, const char mess[]);
+
+
+double getDouble(double min, double max, const char mess[])
+{
+    double num;
+
+    printf("%s", mess);
+
+    while(1)
+    {
+        printf(">>");
+        scanf("%lf", &num);
+        if (min <= num && num <= max)
+        {
+            break;
+        }
+        else
+        {
+            printf(INV_INPUT);
+        }
+    }
+
+    return num;
+}
+
+int getInt(int min, int max, const char mess[])
+{
+    int num;
+
+    printf("%s", mess);
+
+    while(1)
+    {
+        printf(">>");
+        scanf("%d", &num);
+        if (min <= num && num <= max)
+        {
+            break;
+        }
+        else
+        {
+            printf(INV_INPUT);
+        }
+    }
+
+    return num;
+}
+
+#endif