Skip to content

SQL Standards

SQL is often written once and read many times. Optimise for clarity.

Principles

  • Avoid SELECT * — be explicit about the columns you need
  • Use descriptive aliases — c is not a useful alias for customers
  • Document complex logic with inline comments
  • Consistent casing — pick a convention and stick to it

Suggested Tooling

Tool Purpose
sqlfluff SQL linting and formatting, supports multiple dialects
dbt Transformation framework with built-in testing

Enforce linting in CI so style issues are caught before review.

Formatting Guidance

  • One clause per line (SELECT, FROM, WHERE, GROUP BY)
  • Indent continuation lines consistently
  • Use CTEs over nested subqueries for readability
WITH active_customers AS (
    SELECT
        customer_id,
        name,
        created_at
    FROM customers
    WHERE status = 'active'
)

SELECT
    customer_id,
    COUNT(*) AS order_count
FROM orders
JOIN active_customers USING (customer_id)
GROUP BY customer_id

dbt-Specific

  • Write schema tests for every model (not null, unique, relationships)
  • Document models and columns in .yml files
  • Use dbt docs to generate and share documentation

← Technical Excellence ← Engineering Excellence