Saving Data on Android

Important
: Tap the 
START
 button to start a quiz, then stop the app running in 
Android Studio.
Cool! Now, it's time to start working with migrations.
Saving Data on Android
Chapter 10: Migrations with Room
raywenderlich.com
172

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Migra/ons
Before creating your first migrations with Room, you need to learn what migrations 
are, right?
Simply put, a database migration or schema migration is the process of moving your 
data from one database schema to another. There are many reasons why you might 
want to move your data to another database schema. For example, you might need to 
add a new table because you want to implement a new feature. Some data are not 
available and some columns of your database can be removed. Or, the API you're 
invoking provides different information and you want to add some new columns to 
an existing table. Or, other table can be removed because part of an A/B test and you 
need to save space.
The process of migrating your data from one schema to another could be as simple 
as copying data from one table to another or as complex as reorganizing your entire 
database. Either way, properly planning your migrations comes with benefits:
•
Reversible
: Sometimes, you might want to roll back your changes and return to an 
old schema. Without migrations, this process might be a complete nightmare. 
You'd have to manually apply all the changes, and you might not even remember 
how your old database looked.
•
No data loss
: With migrations, it's much easier to move your data from one 
schema to another in a predictable manner without losing data.