31.7. Data Persistence with SQLite in Flutter: Data Deletion

Data persistence is a critical element in most applications. Users expect their information to be kept secure and accessible no matter when or where they use the app. In Flutter, one of the most common ways to persist data is using SQLite, a lightweight SQL database engine that is easy to use and very efficient.

SQLite is a C library that provides a lightweight disc-based database that does not require a separate process to operate. This makes it an excellent choice for apps on devices such as smartphones and tablets where features are limited. In Flutter, we can use the sqflite library to interact with SQLite databases.

In the previous section, we discussed how to insert and retrieve data using SQLite in Flutter. In this chapter, we will focus on how to delete data from an SQLite database.

Data deletion

Deleting data from an SQLite database is a fairly straightforward operation. All we need to do is execute an SQL DELETE statement, which removes records from the specified table that meet a certain condition.

To delete a record, we first need to identify which record we want to remove. This is usually done using the WHERE clause in the DELETE statement to specify a condition that the record must meet. For example, if we wanted to delete a record with a specific ID, we could use a statement like this:

DELETE FROM my_table WHERE id = ?

In this example, the '?' is a parameter that we can replace with the actual ID we want to delete.

Deleting data with sqflite

In Flutter, the sqflite library provides a convenient way to execute SQL statements like this. Here is an example of how we can use sqflite to delete a record:

Future deleteRecord(int id) async {
  final db = await database;

  await db.delete(
    'my_table',
    where: 'id = ?',
    whereArgs: [id],
  );
}

In this example, 'database' is an instance of the database we just opened. sqflite's 'delete' function performs a DELETE statement for us, using the arguments we supply.

The 'where' clause is a string that specifies the condition that records must meet to be deleted. The 'whereArgs' is a list of values ​​that will be replaced by the '?' in the WHERE clause.

It is important to note that the 'delete' function returns a Future. This means that the operation is performed asynchronously, and we need to use 'await' to ensure that it completes before proceeding.

Conclusion

Persisting data with SQLite in Flutter is a broad topic, but we hope this chapter has given you a good understanding of how to delete data from an SQLite database. Remember to always test your delete operations carefully to ensure they are working as expected and not deleting unwanted data.

In the next section, we'll discuss how to update data in an SQLite database. Stay tuned!