[ADD] Multiple CTEs

Author: stivenramireza

classes/30-multiple-ctes.sql

@@ -0,0 +1,20 @@
+WITH 
+	claps_per_post AS (
+		SELECT
+			post_id,
+			SUM(counter)
+		FROM claps
+		GROUP BY post_id
+	),
+	posts_from_2023 AS (
+		SELECT *
+		FROM posts
+		WHERE created_at BETWEEN '2023-01-01' AND '2023-12-31'
+	)
+
+SELECT *
+FROM claps_per_post
+WHERE claps_per_post.post_id IN (
+	SELECT post_id
+	FROM posts_from_2023
+);