Good practice / bad practice: table aliases

Bad

SELECT a.name, b.name, c.amount
FROM customers a
JOIN orders b ON a.id = b.customer_id
JOIN payments c ON b.id = c.order_id
WHERE a.country = 'XX';

Single-letter aliases save keystrokes and burn comprehension under incident pressure.

Better

SELECT cust.name,
       ord.ordered_at,
       pay.amount
FROM customers AS cust
JOIN orders AS ord
  ON ord.customer_id = cust.id
JOIN payments AS pay
  ON pay.order_id = ord.id
WHERE cust.country = 'XX';

Rules

1. Alias whenever you join; qualify every column
2. Reuse the same alias for a table across the codebase
3. Prefer short pronounceable tokens (cust, ord) over ciphers
4. In correlated subqueries, aliases prevent outer-column mistakes

Style does not replace indexes. It prevents misreading a join at 02:00.