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Discover how to allow null values in Integer columns when working with SQLite and Android Room in your Android apps.
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This video is based on the question https://stackoverflow.com/q/62718883/ asked by the user 'olivia.dayaram' ( https://stackoverflow.com/u/11370830/ ) and on the answer https://stackoverflow.com/a/62719055/ provided by the user 'Adrian K' ( https://stackoverflow.com/u/9015942/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Allowing Nulls in Integer Column with SQLite and Android Room

When working with databases in Android using SQLite and the Android Room library, you may sometimes run into issues while trying to allow null values in an Integer column. This can be particularly challenging if you aren't sure how to define your data model correctly. In this guide, we’ll break down the problem and walk you through the solution step-by-step.

The Problem

Recently, I encountered an issue while trying to add a new column to an existing database table. Below is the migration code that I used intended to add an Integer column:

[[See Video to Reveal this Text or Code Snippet]]

However, I ran into a frustrating error:

[[See Video to Reveal this Text or Code Snippet]]

The root of this problem was that the migration was expecting notNull=true, even though I wanted to allow null values in the new column. So, can an Integer column have nulls, and how can I make sure that notNull=false?

Understanding int vs Integer

The confusion often arises from the difference between int and Integer in Java:

int: This is a primitive data type that cannot hold a null value. It always requires an initialization to a default value (0 if not set).

Integer: This is a wrapper class for the primitive type int and can hold a null value, as it is an object.

The Key Takeaway

Since int can never be null, if you attempt to map a null value from the database to an int, it will lead to exceptions and issues in your program. Instead, we need to utilize the Integer wrapper class for our column.

Solution: Change Your Entity Class

To resolve this issue, simply update your entity class to use Integer instead of int. Here's how you can modify your code:

[[See Video to Reveal this Text or Code Snippet]]

Why This Works

By changing the newColumn from int to Integer, you allow the column to accept null values. Now, when a row in your database does not have a value for newColumn, it will correctly store a null, and the migration will no longer throw errors.

Conclusion

Allowing null values in an Integer column while working with SQLite and Android Room can sometimes lead to confusion. However, by understanding the distinction between int and Integer and adjusting your entity class accordingly, you can solve these issues efficiently. Remember to always use Integer if you wish to allow null entries in your database columns!

Feel free to share your experiences or questions in the comments below, and happy coding!