solve: Medium faizanxmulla#10, faizanxmulla#11

Author: faizanxmulla

interview-query-solutions/Medium/10-exam-scores.sql

@@ -0,0 +1,10 @@
+SELECT   student_name
+         ,SUM(CASE WHEN exam_id=1 THEN score END) AS exam_1
+         ,SUM(CASE WHEN exam_id=2 THEN score END) AS exam_2
+         ,SUM(CASE WHEN exam_id=3 THEN score END) AS exam_3
+         ,SUM(CASE WHEN exam_id=4 THEN score END) AS exam_4
+FROM     exam_scores
+GROUP BY 1
+
+
+-- NOTE: solved in first attempt itself.

interview-query-solutions/Medium/11-duplicate-rows.sql

@@ -0,0 +1,17 @@
+-- Solution 1: using HAVING clause
+
+SELECT   id, name, created_at
+FROM     users
+GROUP BY 1, 2, 3
+HAVING   COUNT(*) > 1
+
+
+-- Solution 2: using ROW_NUMBER() function
+
+WITH CTE as (
+	SELECT *, ROW_NUMBER() OVER(PARTITION BY id ORDER BY created_at) as rn
+	FROM   users
+    )
+SELECT id, name, created_at
+FROM   CTE
+WHERE  rn > 1