Chapter_16th_sql_example2.py

# -*- coding: utf-8 -*-
"""
Created on Fri Aug 7 14:25:45 2020

@author: sana.rasheed
"""

### Chapter 16th - SQLite

# Example 2 
# Functions implementated for quick DB connection and Table creations 
import sqlite3
from sqlite3 import Error 

# Function to open DB connection
def create_connection(db_file):
 """ create a database connection to the SQLite database specified by db_file
 :param db_file: database file
 :return: Connection object or None
 """
 conn = None
 try: 
 conn = sqlite3.connect(db_file)
 print("The SQLite connection is connected")
 return conn
 except Error as e:
 print(e)
 return conn

# Function to close DB connection
def close_connection(conn):
 """ close database connection to the SQLite database specified by db_file
 :param db_file: database file
 """ 
 if (conn):
 conn.close()
 print("The SQLite connection is closed")


# Function to create new table in DB
def create_table_in_db(conn, create_table_sql):
 """ create a table from the create_table_sql statement
 :param conn: Connection object
 :param create_table_sql: a CREATE TABLE statement
 :return:
 """ 
 try:
 c = conn.cursor()
 c.execute(create_table_sql) 
 except Error as e:
 print(e)

# Create STUDENT Table 
def create_table():
 database = r"C:\\tempdir\database.db"
 sql_create_projects_table = """ CREATE TABLE IF NOT EXISTS STUDENTS (
 		id integer PRIMARY KEY,
 		name text NOT NULL,
 gpa integer,
 admission_date text
 	); """ 
 # create a database connection
 conn = create_connection(database)
 
 # create tables
 if conn is not None:
 # create projects table
 create_table_in_db(conn, sql_create_projects_table)
 else:
 print("Error! cannot create the database connection.") 
 close_connection(conn)


# main execution to create table
create_table() 

# ======================================================

# Add student data in table
def add_student(conn, student):
 """
 Create a new student entry into the student table
 :param conn:
 :param student:
 :return: student id
 """
 sql = ''' INSERT INTO STUDENTS(name,gpa,admission_date)
 VALUES(?,?,?) '''
 cur = conn.cursor()
 cur.execute(sql, student)
 return cur.lastrowid 

# main function to add student in table
def main_function():
 database =r"C:\\tempdir\database.db"

 # create a database connection
 conn = create_connection(database)
 with conn:
 # add a new student
 student = ('Alan', 1.9, '2019-1-30');
 student_id = add_student(conn, student)
 
 print('The Student ID:', student_id)
 close_connection(conn)

 
# Execute main funtion to add student 'Alan' in table
main_function()


# ==============================================================
### READ TABLE 
database = r"C:\\tempdir\database.db"
#create a database connection
conn = create_connection(database)
try:
 cursor = conn.cursor()
 table_name = "STUDENTS" 
 sql_string = "SELECT * from " + table_name
 sqlite_select_query = sql_string

 cursor.execute(sqlite_select_query)
 records = cursor.fetchall()
 print("Total rows are: ", len(records))
 cursor.close()
except sqlite3.Error as error:
 print("Failed to read data from sqlite table", error)
finally:
 close_connection(conn)		
print(records)