Files for the issue #SQL-348 (#251)

* Create grouping_data.sql

* Add files for the tutorial SUM_groupby_id

* Rename complex_aggregation_example.sql to complex-aggregation-example.sql

* Rename filter_group_result.sql to filter-group-result.sql

* Rename grouping_data.sql to grouping-data.sql

* Rename handling_null_values.sql to handling-null-values.sql

* Rename the folder name for the issue

* Delete .vscode directory

Author: araromi2

sql-queries-6/SUM-groupby-id/complex-aggregation-example.sql

@@ -0,0 +1,5 @@
+SELECT s.id, s.name, SUM(c.credits) AS student_credits
+FROM Student s
+LEFT JOIN Registration r ON s.id = r.student_id
+LEFT JOIN Course c ON r.course_id = c.id
+GROUP BY s.id, s.name;

sql-queries-6/SUM-groupby-id/filter-group-result.sql

@@ -0,0 +1,4 @@
+SELECT department_id, SUM(credits) AS dept_total_credits
+FROM Course
+GROUP BY department_id
+HAVING SUM(credits) > 80;

sql-queries-6/SUM-groupby-id/grouping-data.sql

@@ -0,0 +1,3 @@
+SELECT department_id, SUM(credits) AS dept_total_credits
+FROM Course
+GROUP BY department_id;

sql-queries-6/SUM-groupby-id/handling-null-values.sql

@@ -0,0 +1,5 @@
+SELECT s.id, s.name, SUM(COALESCE(c.credits, 0)) AS student_credits
+FROM Student s
+LEFT JOIN Registration r ON s.id = r.student_id
+LEFT JOIN Course c ON r.course_id = c.id
+GROUP BY s.id, s.name;