Choose a join pattern based on row preservation and metric grain.
Place each situation in the join pattern that matches the intent. INNER JOIN: require a match LEFT JOIN: preserve left rows Pre-aggregate before joining Orders report should include only orders tied to a known customer record. Revenue by product line where every valid line must have a product_id. Accounts report must show accounts with zero tickets. Campaign list must show coupons even if no order used them. Order revenue is stored on orders, but line items are one-to-many. Customers have many tags and many invoices; you need invoice revenue by customer tier.
Sign up free — one personalized lesson every day, matched to your role and goals.
Already have an account? Sign in