GA4 Analytics Showcase
Google Merchandise Store

// Clear ecommerce — always before any ecommerce push
dataLayer.push({ ecommerce: null });

// view_item — fires when product detail page loads
dataLayer.push({
  event: 'view_item',
  ecommerce: {
    currency: 'USD',
    value:    29.99,
    items: [{
      item_id:        'SKU-12345',
      item_name:      'Google Unisex Eco Tee Black',
      item_brand:     'Google',
      item_category:  'Apparel',   // maps to category in BigQuery items[]
      item_category2: 'Mens',
      item_variant:   'Black / L',
      price:          29.99,
      quantity:       1,
      index:          0           // position in list (for list attribution)
    }]
  }
});

// ─── Consent Mode v2 ────────────────────────────────────────────────────
// MUST execute BEFORE the GTM snippet loads. Sets the default deny state.
// GA4 will fire cookieless pings for denied users and use behavioural
// modelling to fill the measurement gap (requires 1,000 daily events).

window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}

gtag('consent', 'default', {
  analytics_storage:   'denied',   // GA4 measurement
  ad_storage:          'denied',   // Google Ads cookies
  ad_user_data:        'denied',   // Enhanced Conversions user data
  ad_personalization:  'denied',   // Remarketing
  wait_for_update:      500        // ms to wait for CMP callback
});

// GTM container loads here...

// When user ACCEPTS in CMP callback:
gtag('consent', 'update', {
  analytics_storage:  'granted',
  ad_storage:         'granted',
  ad_user_data:       'granted',
  ad_personalization: 'granted'
});

-- GA4 Ecommerce Funnel — BigQuery SQL
-- Uses QueryPriority.BATCH (see batch_extractor.py) for zero slot cost
-- _TABLE_SUFFIX wildcard restricts scan to the 92-day analysis window

WITH user_steps AS (
  SELECT
    user_pseudo_id,
    MAX(CASE WHEN event_name = 'view_item'         THEN 1 END) AS s1,
    MAX(CASE WHEN event_name = 'add_to_cart'       THEN 1 END) AS s2,
    MAX(CASE WHEN event_name = 'begin_checkout'    THEN 1 END) AS s3,
    MAX(CASE WHEN event_name = 'purchase'          THEN 1 END) AS s4
  FROM `bigquery-public-data.ga4_obfuscated_sample_ecommerce.events_*`
  WHERE _TABLE_SUFFIX BETWEEN '20201101' AND '20210131'
  GROUP BY user_pseudo_id
)
SELECT step, label, COUNTIF(flag=1) AS users
FROM (
  SELECT 1 step,'view_item' label, s1 flag FROM user_steps UNION ALL
  SELECT 2,'add_to_cart',       s2       FROM user_steps UNION ALL
  SELECT 3,'begin_checkout',    s3       FROM user_steps UNION ALL
  SELECT 4,'purchase',          s4       FROM user_steps
)
GROUP BY step, label ORDER BY step;