- name: cost_per_acquisition
  display_name: Cost per Acquisition
  category: marketing
  type: ratio
  unit: USD
  grain: monthly
  time_column: start_date
  table: campaigns
  tables:
    - campaigns
    - customers
  expression: "SUM(spend) / NULLIF(COUNT(DISTINCT new_customer_id), 0)"
  description: "Average cost to acquire one new customer through marketing campaigns. Compares total campaign spend to the number of new customer registrations attributed to those campaigns."
  dimensions:
    - campaign_type
    - channel
    - region
  notes:
    - "Only counts first-time customers (no repeat purchasers)"
    - "Joins campaigns to customers via attribution tracking"
    - "CPA below customer lifetime value indicates sustainable growth"
  synonyms:
    - cpa
    - customer_acquisition_cost
    - cac
  sql: |
    SELECT
        DATE_TRUNC('month', c.start_date) AS month,
        SUM(c.spend) AS total_spend,
        COUNT(DISTINCT cust.customer_id) AS new_customers,
        ROUND(
            SUM(c.spend) / NULLIF(COUNT(DISTINCT cust.customer_id), 0), 2
        ) AS cost_per_acquisition
    FROM campaigns c
    LEFT JOIN customers cust
        ON cust.attribution_campaign = c.campaign_id
        AND cust.is_first_purchase = true
    GROUP BY 1
    ORDER BY 1
  sql_by_channel: |
    SELECT
        c.channel,
        SUM(c.spend) AS total_spend,
        COUNT(DISTINCT cust.customer_id) AS new_customers,
        ROUND(
            SUM(c.spend) / NULLIF(COUNT(DISTINCT cust.customer_id), 0), 2
        ) AS cpa
    FROM campaigns c
    LEFT JOIN customers cust
        ON cust.attribution_campaign = c.campaign_id
        AND cust.is_first_purchase = true
    GROUP BY 1
    ORDER BY 4