Django - makemigrations - No changes detected
The Best Thing You can do is, Delete the existing database. In my case, I were using phpMyAdmin SQL database, so I manually delete the created database overthere. 
After Deleting:
I create database in PhpMyAdmin, and doesn,t add any tables.
Again run the following Commands:
python manage.py makemigrations
python manage.py migrate
After These Commands:  You can see django has automatically created other necessary tables in Database(Approx there are 10 tables).
python manage.py makemigrations <app_name>
python manage.py migrate
And Lastly: After above commands all the model(table) you have created are directly imported to the database.
Hope this will help.
I was trying to create migrations within an existing app using the makemigrations command but it outputs "No changes detected".
Usually I create new apps using the startapp command but did not use it for this app when I created it.
After debugging, I found that it is not creating migration because the migrations package/folder is missing from an app. 
Would it be better if it creates the folder if it is not there or am I missing something?