1 files changed, 34 insertions, 0 deletions
diff --git a/content/posts/postgres-aggregates/merging-ctes.sql b/content/posts/postgres-aggregates/merging-ctes.sql
new file mode 100644
index 0000000..2061efd
--- /dev/null
+++ b/content/posts/postgres-aggregates/merging-ctes.sql
@@ -0,0 +1,34 @@
+EXPLAIN (
+  ANALYZE,
+  COSTS,
+  VERBOSE,
+  BUFFERS
+) WITH product_reviews AS (
+  SELECT
+    product_id,
+    COUNT(id) AS num_reviews
+  FROM
+    reviews
+  GROUP BY
+    product_id),
+  product_orders AS (
+    SELECT
+      product_id,
+      COUNT(id) AS num_orders
+    FROM
+      orders
+    GROUP BY
+      product_id
+)
+  SELECT
+    products.id,
+    products.name,
+    COALESCE(product_reviews.num_reviews, 0) AS num_reviews,
+  COALESCE(product_orders.num_orders, 0) AS num_orders
+FROM
+  products
+  LEFT JOIN product_reviews ON products.id = product_reviews.product_id
+  LEFT JOIN product_orders ON products.id = product_orders.product_id;
+
+-- WHERE
+--   products.id % 10 = 0