Why should you care?

A Swiggy order line, a Flipkart SKU, and a bank ledger entry each map to rows in a well-named table — bad table design slows every feature.

See it live — copy this example

Run in MySQL Workbench or the mysql CLI.

USE DataFlow;
CREATE TABLE IF NOT EXISTS customers (
  customer_id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  full_name   VARCHAR(120) NOT NULL,
  city        VARCHAR(60),
  created_at  TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

What happened?

• customer_id auto-increments and is the primary key.
• full_name is required; city optional.
• created_at defaults to insert time.
• This is the base table for many DataFlow queries later.

Practice next

1. Run the CREATE TABLE in Workbench.
2. Run DESCRIBE customers; to see columns.
3. Insert one row: INSERT INTO customers (full_name, city) VALUES ('Priya Sharma', 'Pune');
4. Add email VARCHAR(190) UNIQUE NOT NULL and insert a duplicate to see the error.
5. Run SHOW CREATE TABLE customers\G for exact DDL.

Remember

Tables = columns + rows. PRIMARY KEY defines InnoDB row order. DESCRIBE shows structure quickly.

DataFlow customer signup

Registration API inserts one row into customers when a user completes OTP.

Outcome: Every downstream order links via customer_id.