Unit 2.4b Using Programs with Data, SQL
Using Programs with Data is focused on SQL and database actions. Part B focuses on learning SQL commands, connections, and curses using an Imperative programming style,
| Home | API | Notes |
Database Programming is Program with Data
Each Tri 2 Final Project should be an example of a Program with Data.
Prepare to use SQLite in common Imperative Technique
- Explore SQLite Connect object to establish database connection- Explore SQLite Cursor Object to fetch data from a table within a database
Schema of Users table in Sqlite.db
Uses PRAGMA statement to read schema.
Describe Schema, here is resource Resource- What is a database schema?
- What is the purpose of identity Column in SQL database?
- What is the purpose of a primary key in SQL database?
- What are the Data Types in SQL table?
import sqlite3
database = 'instance/sqlite.db' # this is location of database
def schema():
# Connect to the database file
conn = sqlite3.connect(database)
# Create a cursor object to execute SQL queries
cursor = conn.cursor()
# Fetch results of Schema
results = cursor.execute("PRAGMA table_info('users')").fetchall()
# Print the results
for row in results:
print(row)
# Close the database connection
conn.close()
schema()
Reading Users table in Sqlite.db
Uses SQL SELECT statement to read data
- What is a connection object? After you google it, what do you think it does?
- Same for cursor object?
- Look at conn object and cursor object in VSCode debugger. What attributes are in the object?
- Is "results" an object? How do you know?
import sqlite3
def read():
# Connect to the database file
conn = sqlite3.connect(database)
# Create a cursor object to execute SQL queries
cursor = conn.cursor()
# Execute a SELECT statement to retrieve data from a table
results = cursor.execute('SELECT * FROM users').fetchall()
# Print the results
if len(results) == 0:
print("Table is empty")
else:
for row in results:
print(row)
# Close the cursor and connection objects
cursor.close()
conn.close()
read()
import sqlite3
def create():
name = input("Enter your name:")
uid = input("Enter your user id:")
password = input("Enter your password")
dob = input("Enter your date of birth 'YYYY-MM-DD'")
# Connect to the database file
conn = sqlite3.connect(database)
# Create a cursor object to execute SQL commands
cursor = conn.cursor()
try:
# Execute an SQL command to insert data into a table
cursor.execute("INSERT INTO users (_name, _uid, _password, _dob) VALUES (?, ?, ?, ?)", (name, uid, password, dob))
# Commit the changes to the database
conn.commit()
print(f"A new user record {uid} has been created")
except sqlite3.Error as error:
print("Error while executing the INSERT:", error)
# Close the cursor and connection objects
cursor.close()
conn.close()
create()
import sqlite3
def update():
uid = input("Enter user id to update")
dob = input("Enter your date of birth 'YYYY-MM-DD'")
password = input("Enter updated password")
if len(password) < 2:
message = "hacked"
password = 'gothackednewpassword123'
else:
message = "successfully updated"
# Connect to the database file
conn = sqlite3.connect(database)
# Create a cursor object to execute SQL commands
cursor = conn.cursor()
try:
# Execute an SQL command to update data in a table
# Trying to add dob right now...
cursor.execute("UPDATE users SET _password = ?, _dob = ? WHERE _uid = ?", (password, dob, uid))
if cursor.rowcount == 0:
# The uid was not found in the table
print(f"No uid {uid} was not found in the table")
else:
print(f"The row with user id {uid} the password has been {message}")
conn.commit()
except sqlite3.Error as error:
print("Error while executing the UPDATE:", error)
# Close the cursor and connection objects
cursor.close()
conn.close()
update()
import sqlite3
def delete():
uid = input("Enter user id to delete")
# Connect to the database file
conn = sqlite3.connect(database)
# Create a cursor object to execute SQL commands
cursor = conn.cursor()
try:
cursor.execute("DELETE FROM users WHERE _uid = ?", (uid,))
if cursor.rowcount == 0:
# The uid was not found in the table
print(f"No uid {uid} was not found in the table")
else:
# The uid was found in the table and the row was deleted
print(f"The row with uid {uid} was successfully deleted")
conn.commit()
except sqlite3.Error as error:
print("Error while executing the DELETE:", error)
# Close the cursor and connection objects
cursor.close()
conn.close()
delete()
def menu():
operation = input("Enter: (C)reate (R)ead (U)pdate or (D)elete or (S)chema")
if operation.lower() == 'c':
create()
elif operation.lower() == 'r':
read()
elif operation.lower() == 'u':
update()
elif operation.lower() == 'd':
delete()
elif operation.lower() == 's':
schema()
elif len(operation)==0: # Escape Key
return
else:
print("Please enter c, r, u, or d")
menu() # recursion, repeat menu
try:
menu() # start menu
except:
print("Perform Jupyter 'Run All' prior to starting menu")
Hacks
- Add this Blog to you own Blogging site. In the Blog add notes and observations on each code cell.
- In this implementation, do you see procedural abstraction?
- In 2.4a or 2.4b lecture
- Do you see data abstraction? Complement this with Debugging example.
- Use Imperative or OOP style to Create a new Table or do something that applies to your CPT project.
Reference... sqlite documentation
import sqlite3
database = 'instance/cars.db' # this is location of database
def schema():
# Connect to the database file
conn = sqlite3.connect(database)
# Create a cursor object to execute SQL queries
cursor = conn.cursor()
# Fetch results of Schema
results = cursor.execute("PRAGMA table_info('cars')").fetchall()
# Print the results
for row in results:
print(row)
# Close the database connection
conn.close()
schema()
import sqlite3
database = 'instance/cars.db'
def create():
make = input("Enter the make of the car:")
model = input("Enter the model:")
price = input("Enter the price:")
year = input("Enter the year:")
desc = input("Enter a description of the car:")
body_style = input("Enter the body style of the car:")
engine = input("Enter the engine type:")
owner = input("Who's the owner of the car?")
# Connect to the database file
conn = sqlite3.connect(database)
# Create a cursor object to execute SQL commands
cursor = conn.cursor()
try:
# Execute an SQL command to insert data into a table
cursor.execute("INSERT INTO cars (_make, _model, _price, _year, _desc, _body_style, _engine, _owner) VALUES (?, ?, ?, ?, ?, ?, ?, ?)", (make, model, price, year, desc, body_style, engine, owner))
# Commit the changes to the database
conn.commit()
print(f"A new car has been added")
except sqlite3.Error as error:
print("Error while executing the INSERT:", error)
# Close the cursor and connection objects
cursor.close()
conn.close()
create()
import sqlite3
def read():
# Connect to the database file
conn = sqlite3.connect(database)
# Create a cursor object to execute SQL queries
cursor = conn.cursor() # open connection object: contains methods and attributes you need to alter data
# Execute a SELECT statement to retrieve data from a table
results = cursor.execute('SELECT * FROM cars').fetchall() #results is an object
# Print the results
if len(results) == 0:
print("Table is empty")
else:
for row in results:
print(row)
# Close the cursor and connection objects
cursor.close()
conn.close()
read()
import sqlite3
database = 'instance/cars.db'
# Take the inputs for each attribute
def update():
id = input("Enter the id of the car:")
make = input("Enter the make of the car:")
model = input("Enter the model:")
price = input("Enter the price:")
year = input("Enter the year:")
desc = input("Enter a description of the car:")
body_style = input("Enter the body style of the car:")
engine = input("Enter the engine type:")
owner = input("Who's the owner of the car?")
# Connect to the database file
conn = sqlite3.connect(database)
# Create a cursor object to execute SQL commands
cursor = conn.cursor()
try:
# Execute an SQL command to update data in a table
# Trying to add dob right now...
cursor.execute("UPDATE cars SET _make = ?, _model = ?, _price = ?, _year = ?, _desc = ?, _body_style = ?, _engine = ?, _owner = ? WHERE id = ?", (make, model, price, year, desc, body_style, engine, owner, id))
if cursor.rowcount == 0:
# Car ID not found
print(f"No id was found in the table")
# Commit new data
else:
print(f"Car with the id {id} has been updated")
conn.commit()
except sqlite3.Error as error:
print("Error while updating the record:", error)
# Close the cursor and connection objects
cursor.close()
conn.close()
update()
import sqlite3
def delete():
id = input("Select the ID of the car you wish to remove: ")
# Connect to the database file
conn = sqlite3.connect(database)
# Create a cursor object to execute SQL commands
cursor = conn.cursor()
# Validate the input
try:
id = int(id)
except ValueError:
print("Invalid input: ID must be an integer.")
return
try:
# Use a parameterized query to prevent SQL injection
c = conn.cursor()
c.execute("DELETE FROM cars WHERE id = ?", (id,))
conn.commit()
print(f"Row with ID {id} has been deleted.")
except sqlite3.Error as e:
print(f"Error deleting row with ID {id}: {e}")
finally:
# Close the connection
cursor.close
conn.close()
delete()
def menu():
operation = input("Enter: (C)reate (R)ead (U)pdate or (D)elete or (S)chema")
if operation.lower() == 'c':
create()
elif operation.lower() == 'r':
read()
elif operation.lower() == 'u':
update()
elif operation.lower() == 'd':
delete()
elif operation.lower() == 's':
schema()
elif len(operation)==0: # Escape Key
return
else:
print("Please enter c, r, u, or d")
menu() # recursion, repeat menu
try:
menu() # start menu
except:
print("Perform Jupyter 'Run All' prior to starting menu")
def menu():
options = ['c', 'r', 'u', 'd', 's']
operation = input("Enter: (C)reate (R)ead (U)pdate or (D)elete or (S)chema")
if operation.lower() in options:
if operation.lower() == 'c':
create()
elif operation.lower() == 'r':
read()
elif operation.lower() == 'u':
update()
elif operation.lower() == 'd':
delete()
elif operation.lower() == 's':
schema()
elif len(operation) == 0: # Escape Key
return
else:
print("Please enter c, r, u, or d")
menu() # recursion, repeat menu
try:
menu() # start menu
except:
print("Perform Jupyter 'Run All' prior to starting menu")