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Adding, Reading, Updating, Deleting

You have a table. Now let's put data in it, read it back, change it, and remove it. These four operations — often called CRUD (Create, Read, Update, Delete) — are everything you do with a database.

All the examples below assume database.py already has the connection, the Patient model, and create_table(). You run each snippet in a separate main.py that imports Patient from it:

# main.py
from database import Patient

Add — create()

from database import Patient

Patient.objects.create(name="Alice", age=24)
Patient.objects.create(name="Bob",   age=31)
Patient.objects.create(name="Carol", age=19)

Each call adds one row to the patients table. Run this and the data is saved permanently — stop the program, start it again, and the records are still there.

Read all — all()

from database import Patient

patients = Patient.objects.all()

for patient in patients:
    print(patient.name, patient.age)

all() returns every row in the table. You loop through them just like a Python list. Each item is a Patient object — access its fields with dot notation: patient.name, patient.age.

Read one — get()

from database import Patient

patient = Patient.objects.get(id=1)
print(patient.name)

get() fetches a single row that matches the condition. Use id to find a specific record by its unique number.

Filter — filter()

from database import Patient

results = Patient.objects.filter(name="Alice")

for patient in results:
    print(patient.name, patient.age)

filter() returns all rows that match. You can filter by any field.

Update — bulk_update()

from database import Patient

Patient.objects.filter(id=1).bulk_update(age=25)

Chain filter() to find the row you want, then call bulk_update() with the new values. This updates every row that the filter matched — here just the one with id=1.

Delete — delete()

from database import Patient

Patient.objects.filter(id=1).delete()

Same pattern — filter to find the row, then call delete(). That row is permanently removed from the table.

The full picture

# main.py
from database import Patient

# Add
Patient.objects.create(name="Alice", age=24)
Patient.objects.create(name="Bob",   age=31)

# Read all
for p in Patient.objects.all():
    print(p.id, p.name, p.age)

# Update
Patient.objects.filter(id=1).bulk_update(age=25)

# Confirm update
alice = Patient.objects.get(id=1)
print("Updated age:", alice.age)

# Delete
Patient.objects.filter(id=2).delete()

# Confirm delete
print("Remaining:", Patient.objects.all().count())

Run this. Watch the output. Every operation touches the actual .sqlite3 file — stop and restart the program and the remaining data is still there.

Challenge

In main.py, write a short script that:

  1. Adds three patients
  2. Prints all of them
  3. Updates the age of the first one
  4. Deletes the second one
  5. Prints all remaining patients

Stop and restart main.py. Do the remaining patients still show? They should.

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