Database Design for Your First App

A database is easier to work with when its structure reflects the app's actual rules. Asking AI to create whatever tables are needed often produces hidden assumptions that surface later as duplicated records or broken permissions.

Start with the objects your first workflow needs. For a private task app, those may be users and tasks, with each task associated with one owner.

Describe the records in plain language

Write what one row represents. A task row describes one task, not a user, a whole project, or a list of unrelated titles.

Then identify the fields that matter: a task ID, owner ID, title, and completion state. Avoid adding fields merely because a generated schema looks more professional with them.

Define what is required, what can be empty, and what each identifier points to.

Give each record a stable identity

A primary key distinguishes a row. A title is usually a poor identifier because two tasks can share the same title and a title can change.

A foreign key expresses a relationship to another table. For example, an owner ID can reference a user record.

PostgreSQL constraints can enforce required values, uniqueness, relationships, and specified conditions. They help protect data consistency, but they do not decide which signed-in caller is allowed to access a row.

Examine a small schema

The following illustrative PostgreSQL schema describes a minimal structure. It is a starting point for discussion, not a complete account or authentication implementation.

CREATE TABLE app_users (
  id text PRIMARY KEY
);

CREATE TABLE tasks (
  id text PRIMARY KEY,
  owner_id text NOT NULL REFERENCES app_users(id),
  title text NOT NULL CHECK (length(trim(title)) > 0),
  completed boolean NOT NULL DEFAULT false
);

The schema rejects a missing owner reference and a title consisting only of spaces under the database's trim behavior. It does not establish that the caller is the owner.

Production requirements may need additional title rules, timestamps, indexes, and explicit deletion behavior. Define those decisions rather than assuming the model selected them correctly.

Keep ownership separate from authorization

An owner_id field records a relationship. It is not a security boundary by itself.

The application must associate a validated caller with the appropriate records and enforce permissions for each protected action. A request should not become authorized simply because it supplies an existing owner's ID.

If you add shared projects, define membership and roles explicitly. Do not overload one owner field to represent several different access relationships.

Test the data rules

In a disposable development database, try the intended valid records and representative invalid cases.

A task referencing a missing user should be rejected. A duplicate primary key should not silently create another record. A valid title should remain intact.