[Django]-How to create a new table using model

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10đź‘Ť

âś…

First, create a backup of your database. Copy it to your development machine. Try things out on that. That way it doesn’t matter if it does go “boom” for some reason.

The first thing to do is

python manage.py showmigrations

This shows all the existing migrations, and it should show that they have been applied with an [X].

Then,

python manage.py makemigrations

Makes a new migration file for your new model (name 00004_…).

Then do

python manage.py migrate

to apply it. To undo it, go back to the state of migrations 00003, with

python manage.py migrate <yourappname> 00003
👤RemcoGerlich

4đź‘Ť

There are two steps to migrations in Django. 

./manage.py makemigrations

will create the migration files that you see – these describe the changes that should be made to the database.

You also need to run 

./manage.py migrate

this will apply the migrations and actually run the alter table commands in SQL to change the actual database structure.

Generally adding fields or tables won’t affect anything else in the database. Be more careful when altering or deleting existing fields as that can affect your data.

The reason for two steps is so that you can make changes on a dev machine and once happy commit the migration files and release to your production environment. Then you run the migrate command on your production machine to bring the production database to the same state as your dev machine (no need for makemigrations on production assuming that your databases started the same).

👤wobbily_col

2đź‘Ť

My question is now how do I “create” this boom table using the
migration script and the boom model?

 ./manage.py makemigrations

I am worried that I might accidentally disrupt anything that is
already in DB.

The whole point of migrations, is that it doesn’t

I know that it has something to do with manage.py and running migrate
or runmigration

For more information please refer to : https://docs.djangoproject.com/en/1.10/topics/migrations/

And rest assured that your database will not go boom! 🙂

👤e4c5

1đź‘Ť

I solved it simply, changing the name of the new model to the original name, and then I checked if there is the table in the database, if not, I just create a new table with the old name with just a field like id.
And then clear migrations and create new migrations, migrate and verify table was fixed in DB and has all missing fields.
If it still doesn’t work, then change the model name back to a new one.
but when django asks you if you are renaming the model you should say NO to get the old one removed properly and create a new one.

This type of error usually occurs when you delete some table in dB manually, and then the migration history changes in the tables are lost.
But it is not necessary to erase the entire database and start from scratch.

👤Rubén Vázquez

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