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,
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")
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
cursor.execute("UPDATE users SET _password = ? WHERE _uid = ?", (password, 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
- What is a database schema? A databse schema is a place where a cateogory with functions is for example table users/ id/pass are all defined within this one.
- What is the purpose of identity Column in SQL database? The identity column allows to set a column wihtin a table where all the tings are identitfied within.
- What is the purpose of a primary key in SQL database? A primary key is the first colimn in a dablt
- What are the Data Types in SQL table? The data types are integer, string.
What is a connection object? After you google it, what do you think it does?
- Same for cursor object? It bakes a conections to the data object and it puts a cursor into the terminal.
- Look at conn object and cursor object in VSCode debugger. What attributes are in the object? the atributs are classes and other objects.
- Is "results" an object? How do you know? No becuase why would it it allows you to deine the result as a result in an object a result should be an output
- Compore create() in both SQL lessons. What is better or worse in the two implementations? One goes through OOP calling the objects others take it from its own functions kown as imperative.
- Explain purpose of SQL INSERT. Is this the same as User init?
- THe purpose is to be same as init in order to create something
- What does the hacked part do? THe hacked part is after the condinitons
- Explain try/except, when would except occur? like a conditial it its = to the else part
- What code seems to be repeated in each of these examples to point, why is it repeated? the calling of functions to establsih what teh output should be.
Uses a delete function to remove a user based on a user input of the id.
- Is DELETE a dangerous operation? Why? No it is helpful and you can always re add data
- In the print statemements, what is the "f" and what does {uid} do? THis is an f string which allows to call the variable and print it.
- Why does the menu repeat? This menu reapeats in roder to continue to call the lists
- Could you refactor this menu? Make it work with a List?