makemigrations and migrate commands in Django - Step-by-Step Execution

Concept Flow - makemigrations and migrate commands

Write or change models.py

↓

Run: python manage.py makemigrations

↓

Create migration files

↓

Run: python manage.py migrate

↓

Apply migrations to database

↓

Database schema updated

This flow shows how changes in Django models create migration files, which are then applied to update the database schema.

Execution Sample

Django

python manage.py makemigrations
python manage.py migrate

These commands create migration files from model changes and apply them to the database.

Execution Table

Step	Command	Action	Result
1	makemigrations	Detect changes in models.py	Creates new migration file(s)
2	makemigrations	No changes detected	No new migration files created
3	migrate	Apply all unapplied migrations	Database schema updated
4	migrate	No unapplied migrations	No changes to database
5	Exit	All migrations applied	Database is up to date

💡 No more migrations to apply, database schema matches models

Variable Tracker

Variable	Start	After makemigrations 1	After migrate 1	Final
migration_files	[]	[0001_initial.py]	[0001_initial.py]	[0001_initial.py]
database_schema	empty	empty	updated with new tables	updated with new tables
models.py	defined models	defined models	defined models	defined models

Key Moments - 3 Insights

Why does running 'makemigrations' sometimes create no new files?

Because no changes were made to models.py since the last migration, as shown in execution_table step 2.

What happens if you run 'migrate' without any new migration files?

No changes are applied to the database since all migrations are already applied, as shown in execution_table step 4.

Why do we need to run both 'makemigrations' and 'migrate'?

'makemigrations' creates migration files from model changes, and 'migrate' applies those files to update the database, shown in steps 1 and 3.

Visual Quiz - 3 Questions

Look at the execution table, what is created after running 'makemigrations' when models change?

A Database schema updated

B New migration file(s)

C No changes

D Models.py file

💡 Hint

Refer to execution_table row 1 where makemigrations creates migration files

At which step does the database schema get updated?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at execution_table row 3 where migrate applies migrations

If you change models.py but forget to run 'makemigrations', what happens when you run 'migrate'?

A No migration files to apply, so no database change

B Database updates with new schema

C Error occurs

D New migration files are created automatically

💡 Hint

Check variable_tracker and execution_table steps 1 and 3 for migration file creation and application

Concept Snapshot

Django migrations update your database schema.
Run 'makemigrations' to create migration files from model changes.
Run 'migrate' to apply these files to the database.
No model changes means no new migration files.
Migrations keep your database and models in sync.

Full Transcript

In Django, when you change your models.py file, you need to update your database schema to match. First, you run 'python manage.py makemigrations' which looks at your models and creates migration files describing the changes. If no changes are found, no new files are created. Next, you run 'python manage.py migrate' which applies all pending migration files to the database, updating its structure. If there are no new migrations, the database stays the same. This two-step process ensures your database matches your code models.

Practice

1. What is the main purpose of the makemigrations command in Django?

easy

A. To delete old migration files

B. To apply changes to the database

C. To start the Django development server

D. To create migration files that describe changes in models

Solution

1. Step 1: Understand the role of makemigrations

   This command generates files that describe changes made to Django models, like adding or removing fields.

2. Step 2: Differentiate from migrate

   migrate applies those changes to the database, but makemigrations only creates the description files.

3. Final Answer:

   To create migration files that describe changes in models -> Option D

4. Quick Check:

   makemigrations creates files = A [OK]

Hint: Remember: makemigrations creates files, migrate applies them [OK]

Common Mistakes:

• Confusing makemigrations with migrate
• Thinking makemigrations changes the database directly
• Assuming makemigrations starts the server

2. Which of the following is the correct command to apply migrations to the database in Django?

easy

A. python manage.py makemigrations

B. python manage.py migrate

C. python manage.py runserver

D. python manage.py makemigrate

Solution

1. Step 1: Identify the command to apply migrations

   The command python manage.py migrate applies migration files to update the database schema.

2. Step 2: Check other options

   makemigrations creates migration files, runserver starts the server, and makemigrate is not a valid command.

3. Final Answer:

   python manage.py migrate -> Option B

4. Quick Check:

   Apply migrations = migrate = A [OK]

Hint: Use migrate to apply changes, not makemigrations [OK]

Common Mistakes:

• Typing makemigrate instead of migrate
• Using makemigrations to update the database
• Confusing runserver with migration commands

3. Given the following sequence of commands in a Django project:

python manage.py makemigrations
python manage.py migrate

What will happen after running these commands?

medium

A. The database schema will be updated to match the current models

B. The server will start running

C. Migration files will be deleted

D. The models will be reset to default

Solution

1. Step 1: Understand the effect of makemigrations

   This command creates migration files describing model changes.

2. Step 2: Understand the effect of migrate

   This command applies those migration files to update the database schema accordingly.

3. Final Answer:

   The database schema will be updated to match the current models -> Option A

4. Quick Check:

   makemigrations + migrate = update DB schema = C [OK]

Hint: makemigrations then migrate updates database schema [OK]

Common Mistakes:

• Thinking migrate starts the server
• Believing migration files get deleted automatically
• Assuming models reset after migrations

4. You ran python manage.py migrate but got an error saying "No migrations to apply." What is the most likely cause?

medium

A. You forgot to run makemigrations to create migration files

B. The database is corrupted

C. You need to restart the Django server

D. Your models have syntax errors

Solution

1. Step 1: Analyze the error message

   "No migrations to apply" means Django found no new migration files to run.

2. Step 2: Identify the missing step

   If you did not run makemigrations, no migration files exist to apply.

3. Final Answer:

   You forgot to run makemigrations to create migration files -> Option A

4. Quick Check:

   No migrations found = forgot makemigrations = D [OK]

Hint: Run makemigrations before migrate to create migration files [OK]

Common Mistakes:

• Restarting server instead of creating migrations
• Assuming database corruption without checking migrations
• Ignoring missing migration files

5. You added a new field to a Django model but forgot to run makemigrations. Later, you run python manage.py migrate. What will happen?

hard

A. The new field will be added to the database automatically

B. An error will occur because migration files are missing

C. Nothing changes in the database schema

D. Django will create migration files automatically and apply them

Solution

1. Step 1: Understand the role of makemigrations

   This command creates migration files describing model changes like new fields.

2. Step 2: Effect of running migrate without new migration files

   If no migration files exist, migrate finds nothing to apply, so the database stays unchanged.

3. Final Answer:

   Nothing changes in the database schema -> Option C

4. Quick Check:

   No migration files = migrate does nothing = B [OK]

Hint: Always run makemigrations after model changes before migrate [OK]

Common Mistakes:

• Expecting migrate to detect model changes automatically
• Assuming migrate creates migration files
• Thinking database updates without migration files