Creating tables via SQL editor in Supabase - Try It Yourself

Creating tables via SQL editor

📖 Scenario: You are setting up a simple database for a small online bookstore using Supabase. You will create tables to store information about books and authors.

🎯 Goal: Create two tables named authors and books using the Supabase SQL editor. The authors table will store author details, and the books table will store book details including a reference to the author.

📋 What You'll Learn

Create a table called authors with columns author_id (integer, primary key), name (text, not null), and birth_year (integer).

Create a table called books with columns book_id (integer, primary key), title (text, not null), author_id (integer, foreign key referencing authors.author_id), and published_year (integer).

Use appropriate SQL syntax to define primary keys and foreign key constraints.

Ensure the tables are created successfully in the Supabase SQL editor.

💡 Why This Matters

🌍 Real World

Creating tables is the first step in building a database for any application, such as an online bookstore, to store and organize data efficiently.

💼 Career

Database creation and management skills are essential for cloud engineers, backend developers, and data professionals working with cloud databases like Supabase.

1

Create the authors table

Write a SQL statement to create a table called authors with these columns: author_id as an integer primary key, name as text and not null, and birth_year as an integer.

Supabase

-- Write the SQL to create the authors table here
-- Your code here

Hint

Use CREATE TABLE authors (...) and define each column with its type and constraints.

2

Create the books table without foreign key

Write a SQL statement to create a table called books with these columns: book_id as an integer primary key, title as text and not null, author_id as an integer, and published_year as an integer. Do not add the foreign key constraint yet.

Supabase

-- Write the SQL to create the books table here without foreign key
-- Your code here

Hint

Define the books table columns with correct types and primary key, but skip foreign key for now.

3

Add foreign key constraint to books table

Modify the books table creation SQL to add a foreign key constraint on author_id referencing authors.author_id.

Supabase

CREATE TABLE books (
    book_id INTEGER PRIMARY KEY,
    title TEXT NOT NULL,
    author_id INTEGER,
    published_year INTEGER
    -- Your code here
);

Hint

Add REFERENCES authors(author_id) after the author_id INTEGER column definition.

4

Finalize and verify table creation

Ensure both authors and books tables are created with correct columns, primary keys, and foreign key constraint in one SQL script.

Supabase

-- Write the full SQL script to create both authors and books tables with all constraints
-- Your code here

Hint

Make sure the full SQL script includes both table creations with all constraints.

Practice

1. What is the main purpose of the CREATE TABLE statement in Supabase SQL editor?

easy

A. To insert data into an existing table

B. To delete an existing table from the database

C. To update data in an existing table

D. To create a new table with specified columns and data types

Solution

1. Step 1: Understand the purpose of CREATE TABLE

   The CREATE TABLE command is used to make a new table structure in the database.

2. Step 2: Differentiate from other SQL commands

   Deleting, inserting, or updating data uses different commands like DROP TABLE, INSERT INTO, or UPDATE.

3. Final Answer:

   To create a new table with specified columns and data types -> Option D

4. Quick Check:

   CREATE TABLE means create table [OK]

Hint: Remember: CREATE TABLE makes new tables, not data changes [OK]

Common Mistakes:

• Confusing CREATE TABLE with INSERT or UPDATE commands
• Thinking CREATE TABLE deletes tables
• Assuming CREATE TABLE modifies existing data

2. Which of the following is the correct syntax to create a table named users with columns id (integer) and email (text) in Supabase SQL editor?

easy

A. CREATE users TABLE (id INT, email STRING);

B. CREATE TABLE users (id INTEGER, email TEXT);

C. TABLE CREATE users (id INT, email TEXT);

D. CREATE TABLE users id INTEGER, email TEXT;

Solution

1. Step 1: Check the correct SQL syntax for table creation

   The correct syntax is CREATE TABLE table_name (column_name data_type, ...); with parentheses around columns.

2. Step 2: Validate data types and order

   Use INTEGER and TEXT as valid data types. The statement must start with CREATE TABLE followed by the table name.

3. Final Answer:

   CREATE TABLE users (id INTEGER, email TEXT); -> Option B

4. Quick Check:

   Correct SQL syntax = CREATE TABLE users (id INTEGER, email TEXT); [OK]

Hint: Use parentheses and correct data types for columns [OK]

Common Mistakes:

• Missing parentheses around columns
• Wrong order of keywords
• Using invalid data types like STRING instead of TEXT

3. Given the SQL command:

CREATE TABLE products (product_id SERIAL PRIMARY KEY, name TEXT NOT NULL, price NUMERIC);

What will be the behavior of the product_id column?

medium

A. It stores text values

B. It must be manually entered for each new product

C. It will automatically generate a unique number for each new row

D. It allows duplicate values

Solution

1. Step 1: Understand the SERIAL PRIMARY KEY usage

   The SERIAL type auto-increments numbers for new rows, and PRIMARY KEY ensures uniqueness.

2. Step 2: Analyze column behavior

   Because of SERIAL PRIMARY KEY, product_id auto-generates unique numbers; manual entry is not required.

3. Final Answer:

   It will automatically generate a unique number for each new row -> Option C

4. Quick Check:

   SERIAL PRIMARY KEY = auto unique number [OK]

Hint: PRIMARY KEY with SERIAL auto-increments IDs [OK]

Common Mistakes:

• Thinking SERIAL requires manual input
• Assuming duplicates are allowed in PRIMARY KEY
• Confusing data types for this column

4. You wrote this SQL to create a table:

CREATE TABLE orders (order_id INT PRIMARY KEY, order_date DATE, customer_id INT);

The table creates successfully, but when inserting rows without specifying order_id, Supabase gives an error. What is the most likely cause?

medium

A. No SERIAL type for auto-incrementing primary key

B. Missing semicolon at the end of the statement

C. No column defined as UNIQUE

D. Using INT instead of INTEGER for data type

Solution

1. Step 1: Check the primary key column definition

   The order_id is INT PRIMARY KEY but lacks auto-increment, so inserting rows without specifying order_id causes errors.

2. Step 2: Understand SERIAL usage for auto-increment

   Using SERIAL instead of INT for primary key allows automatic unique number generation, preventing insert errors.

3. Final Answer:

   No SERIAL type for auto-incrementing primary key -> Option A

4. Quick Check:

   Primary key needs SERIAL for auto-increment [OK]

Hint: Use SERIAL for auto-increment primary keys [OK]

Common Mistakes:

• Assuming INT auto-increments automatically
• Ignoring missing semicolon errors
• Confusing UNIQUE with PRIMARY KEY requirements

5. You want to create a table employees with columns id (auto-incrementing primary key), name (text, required), and email (text, unique). Which SQL command correctly achieves this in Supabase?

hard

A. CREATE TABLE employees (id SERIAL PRIMARY KEY, name TEXT NOT NULL, email TEXT UNIQUE);

B. CREATE TABLE employees (id INT PRIMARY KEY, name TEXT, email TEXT UNIQUE NOT NULL);

C. CREATE TABLE employees (id SERIAL, name TEXT NOT NULL, email TEXT);

D. CREATE TABLE employees (id INTEGER PRIMARY KEY, name TEXT NOT NULL, email TEXT UNIQUE);

Solution

1. Step 1: Define auto-incrementing primary key

   Use SERIAL PRIMARY KEY for id to auto-generate unique IDs.

2. Step 2: Set constraints for name and email

   name must be NOT NULL to be required; email must be UNIQUE to avoid duplicates.

3. Step 3: Verify all constraints and syntax

   CREATE TABLE employees (id SERIAL PRIMARY KEY, name TEXT NOT NULL, email TEXT UNIQUE); correctly includes all required constraints and syntax.

4. Final Answer:

   CREATE TABLE employees (id SERIAL PRIMARY KEY, name TEXT NOT NULL, email TEXT UNIQUE); -> Option A

5. Quick Check:

   Auto-increment + NOT NULL + UNIQUE = CREATE TABLE employees (id SERIAL PRIMARY KEY, name TEXT NOT NULL, email TEXT UNIQUE); [OK]

Hint: Combine SERIAL, NOT NULL, and UNIQUE for correct constraints [OK]

Common Mistakes:

• Forgetting NOT NULL on required columns
• Using INT without SERIAL for auto-increment
• Missing UNIQUE constraint on email