MySQL workflow

Connect → USE database → inspect with SHOW / DESCRIBE → run SELECT with LIMIT → EXPLAIN slow queries → add indexes in staging.

Exploration

USE practice;
SHOW TABLES;
DESCRIBE orders;
SELECT * FROM orders WHERE status = 'open' LIMIT 10;
EXPLAIN SELECT * FROM orders WHERE customer_id = 42;

Practice: Copy SQL into the mysql client, local MySQL/MariaDB, or DB Fiddle (MySQL dialect).

Safe habits

• Always LIMIT exploratory SELECT on large tables
• Preview UPDATE/DELETE with SELECT … WHERE first
• Run DDL migrations in transactions where possible (InnoDB)
• Separate dev/staging/prod credentials

Sample seed data

CREATE TABLE IF NOT EXISTS products (
  id INT AUTO_INCREMENT PRIMARY KEY,
  sku VARCHAR(32) NOT NULL,
  name VARCHAR(255) NOT NULL,
  price DECIMAL(10,2) NOT NULL
);
INSERT INTO products (sku, name, price) VALUES
  ('A1', 'Widget', 9.99),
  ('B2', 'Gadget', 24.50);

Important interview questions and answers

1. Q: EXPLAIN purpose?
   A: Shows access type (ALL vs ref vs range) and rows examined—index tuning starting point.
2. Q: LIMIT on exploration?
   A: Prevents dumping millions of rows into terminal or GUI.

Self-check

1. What should you run before UPDATE with a new WHERE clause?
2. What does DESCRIBE show?