Do you have practical experience using keys in systems or databases?

Yes, keys are used in systems and databases for the unique identification of records and ensuring data integrity.

For example, in an SQL database:

• Primary Key — a unique identifier for a record.
• Foreign Key — a reference to the primary key of another table to establish relationships.

In Flutter, when working with local databases (such as SQLite via the sqflite package), keys are also used for data identification and relationships.

Example of creating tables with keys in SQLite:

CREATE TABLE users (
  id INTEGER PRIMARY KEY,
  name TEXT NOT NULL
);

CREATE TABLE orders (
  order_id INTEGER PRIMARY KEY,
  user_id INTEGER,
  FOREIGN KEY(user_id) REFERENCES users(id)
);

In Flutter, these keys can be used for data retrieval and updates via SQL queries.