Seed data management in Supabase - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is seed data in the context of a database?

Seed data is the initial set of data loaded into a database to set up default values or test data before the application runs.

beginner

Why is seed data management important in Supabase projects?

It ensures the database starts with consistent data for development, testing, or demos, making it easier to work and avoid errors.

intermediate

How can you add seed data in Supabase using SQL scripts?

You write SQL INSERT statements in a file and run them using Supabase CLI or SQL editor to populate tables with initial data.

intermediate

What is a best practice when managing seed data in a team project?

Keep seed data scripts in version control so everyone uses the same starting data and can update it safely.

intermediate

How does seed data differ from migration scripts?

Migrations change database structure; seed data adds initial content. Both are needed but serve different purposes.

What is the main purpose of seed data?

A To change the database structure

B To delete old data

C To set up initial data in the database

D To backup the database

Seed data is used to add initial data, not to change structure or delete data.

Which tool can you use to run seed SQL scripts in Supabase?

A Supabase CLI

B Docker

C GitHub

D Node.js

Supabase CLI allows running SQL scripts including seed data scripts.

Where should seed data scripts be stored in a project?

A Only on local machines

B In version control (e.g., Git)

C In a private folder outside the project

D In the cloud only

Storing seed scripts in version control ensures team consistency.

What is the difference between seed data and migrations?

A Neither affects the database

B Seed data changes structure; migrations add content

C Both do the same thing

D Seed data adds content; migrations change structure

Seed data populates tables; migrations modify tables or schema.

When is seed data typically used?

A During development and testing

B Only in production

C To delete data

D To backup data

Seed data helps developers and testers by providing initial data.

Explain what seed data is and why it is useful in Supabase projects.

Think about how starting with some data helps when building or testing an app.

Describe best practices for managing seed data in a team environment.

Consider how teams share and maintain code and data.

Practice

1. What is the main purpose of seed data in a Supabase project?

easy

A. To delete all existing data from the database

B. To backup the database before changes

C. To add initial data automatically to the database

D. To monitor database performance

Solution

1. Step 1: Understand seed data concept

   Seed data is used to populate the database with initial or default data automatically.

2. Step 2: Identify the purpose in Supabase

   In Supabase, seed data helps set up consistent data for testing and development.

3. Final Answer:

   To add initial data automatically to the database -> Option C

4. Quick Check:

   Seed data = initial data setup [OK]

Hint: Seed data means initial data added automatically [OK]

Common Mistakes:

• Confusing seed data with backup or monitoring
• Thinking seed deletes data instead of adding
• Assuming seed data is for performance tuning

2. Which command runs seed scripts in a Supabase project?

easy

A. supabase db backup create

B. supabase db migrate run

C. supabase db reset

D. supabase db seed run

Solution

1. Step 1: Recall Supabase seed command

   The command to execute seed scripts is supabase db seed run.

2. Step 2: Differentiate from other commands

   supabase db migrate run applies migrations, not seeds; reset and backup are unrelated.

3. Final Answer:

   supabase db seed run -> Option D

4. Quick Check:

   Seed scripts run with supabase db seed run [OK]

Hint: Seed scripts run with 'supabase db seed run' command [OK]

Common Mistakes:

• Using migrate command instead of seed
• Confusing reset with seed run
• Trying backup commands for seeding

3. Given this seed script snippet in Supabase:

INSERT INTO users (id, name) VALUES (1, 'Alice'), (2, 'Bob');
INSERT INTO users (id, name) VALUES (3, 'Charlie');

What will be the total number of users after running the seed?

medium

A. 3

B. 2

C. 1

D. 4

Solution

1. Step 1: Count inserted rows in first statement

   The first INSERT adds 2 users: Alice and Bob.

2. Step 2: Count inserted rows in second statement

   The second INSERT adds 1 user: Charlie.

3. Step 3: Calculate total users inserted

   Total users = 2 + 1 = 3.

4. Final Answer:

   3 -> Option A

5. Quick Check:

   2 + 1 = 3 users inserted [OK]

Hint: Add all inserted rows to find total users [OK]

Common Mistakes:

• Counting only first INSERT statement
• Assuming duplicate rows overwrite
• Miscounting number of values per INSERT

4. You run supabase db seed run but get an error: duplicate key value violates unique constraint. What is the likely cause?

medium

A. Database connection is lost

B. Seed script tries to insert data with existing primary keys

C. Supabase CLI is not installed

D. Seed script syntax is incorrect

Solution

1. Step 1: Understand the error message

   The error means the seed script tries to insert rows with keys already in the database.

2. Step 2: Identify cause in seed data context

   Duplicate primary keys cause conflicts when inserting seed data multiple times without cleanup.

3. Final Answer:

   Seed script tries to insert data with existing primary keys -> Option B

4. Quick Check:

   Duplicate key error = duplicate primary keys in seed [OK]

Hint: Duplicate key error means repeated primary keys in seed data [OK]

Common Mistakes:

• Assuming syntax error causes duplicate key message
• Blaming CLI installation for data errors
• Ignoring database state before seeding

5. You want to seed a Supabase database with initial users but avoid duplicate entries if the seed runs multiple times. Which approach is best?

hard

A. Use INSERT ... ON CONFLICT DO NOTHING in seed scripts

B. Delete the entire database before each seed run

C. Run seed scripts only once manually

D. Use DROP TABLE users before inserting

Solution

1. Step 1: Understand the problem of duplicates

   Running seed multiple times can cause duplicate key errors if data already exists.

2. Step 2: Choose a safe insert method

   Using INSERT ... ON CONFLICT DO NOTHING skips inserting duplicates safely.

3. Step 3: Evaluate other options

   Deleting database or tables is risky and inefficient; running seed once is error-prone.

4. Final Answer:

   Use INSERT ... ON CONFLICT DO NOTHING in seed scripts -> Option A

5. Quick Check:

   Safe inserts prevent duplicates with ON CONFLICT [OK]

Hint: Use ON CONFLICT DO NOTHING to avoid duplicate inserts [OK]

Common Mistakes:

• Dropping tables can cause data loss
• Assuming seed runs only once always
• Deleting whole database is overkill