understanding-the-Error-Column-Is-Invalid-in-the-Select-List-Because-It-Is-Not-Contained-in-either-an-Aggregate-Function-or-the-Group-by-Clause

Author: samuelkaranja

sql-queries-12/understanding-the-Error-Column-Is-Invalid-in-the-Select-List-Because-It-Is-Not-Contained-in-either-an-Aggregate-Function-or-the-Group-by-Clause/understanding-the-Error-Column-Is-Invalid-in-the-Select-List-Because-It-Is-Not-Contained-in-either-an-Aggregate-Function-or-the-Group-by-Clause-sqlserver.sql

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+-- Understanding the Error
+
+SELECT enrollment_date, name, AVG(gpa) AS average_gpa
+FROM Student 
+GROUP BY enrollment_date;
+
+
+-- Remove the Unaggregated Column From the SELECT Clause
+
+SELECT enrollment_date, AVG(gpa) AS average_gpa
+FROM Student
+GROUP BY enrollment_date;
+
+
+-- Use an Aggregate Function
+
+SELECT enrollment_date, MIN(name) AS example_student, AVG(gpa) AS average_gpa
+FROM Student
+GROUP BY enrollment_date;
+
+
+-- Include the Column in the GROUP BY Clause
+
+SELECT name, enrollment_date, AVG(gpa) AS avg_gpa
+FROM Student
+GROUP BY name, enrollment_date;
+
+
+-- Use a Subquery or CTE
+-- Subquery
+
+SELECT s.*
+FROM Student s
+JOIN (
+    SELECT enrollment_date, MAX(gpa) AS top_gpa
+    FROM Student
+    GROUP BY enrollment_date
+) AS grouped
+ON s.enrollment_date = grouped.enrollment_date
+AND s.gpa = grouped.top_gpa;
+
+-- CTE
+
+WITH TopGPA AS (
+    SELECT enrollment_date, MAX(gpa) AS top_gpa
+    FROM Student
+    GROUP BY enrollment_date
+)
+SELECT s.*
+FROM Student s
+JOIN TopGPA t
+  ON s.enrollment_date = t.enrollment_date
+ AND s.gpa = t.top_gpa;
+ 
+ 
+ -- Use Window Functions for Aggregate Context Without GROUP BY
+ 
+ SELECT
+  id,
+  name,
+  enrollment_date,
+  gpa,
+  AVG(gpa) OVER (PARTITION BY enrollment_date) AS avg_gpa_for_enroll_date
+FROM Student;
+
+