Merge pull request #1 from kaushik-baeldung/kaushik-baeldung-patch-1

SQL Eval Article - kaushik@baeldung.com

Author: kaushik-baeldung

composite_index_eval_article.sql

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+USE University;
+
+-- Difference between Single and Composite Index
+
+-- Explain Single Index
+SELECT *
+FROM University.Student;
+
+DESCRIBE University.Student;
+
+SELECT *
+FROM University.Student
+WHERE national_id = '123345566';
+
+EXPLAIN SELECT *
+FROM University.Student
+WHERE national_id = '123345566';
+
+CREATE INDEX idx_national_id
+ON University.Student (national_id);
+
+EXPLAIN SELECT *
+FROM University.Student
+WHERE national_id = '123345566';
+
+-- Difference between Single and Composite Index
+
+SELECT * 
+FROM University.Registration;
+
+SELECT student_id, course_id, semester, reg_datetime
+FROM University.Registration
+WHERE semester = 'Fall'
+AND student_id = 1001
+ORDER BY 2
+;
+
+EXPLAIN SELECT student_id, course_id, semester, reg_datetime
+FROM University.Registration
+WHERE semester = 'Fall'
+AND student_id = 1001
+ORDER BY 2
+;
+
+CREATE INDEX idx_student_id 
+ON University.Registration (student_id);
+
+CREATE INDEX idx_student_id_semester_course
+ON University.Registration (student_id, semester, course_id);
+
+
+-- Multi-Column Searches
+
+SELECT *
+FROM University.Course;
+
+SELECT *
+FROM University.Faculty;
+
+SELECT *
+FROM University.Department;
+
+SHOW INDEXES IN University.Course;
+
+SELECT id 
+FROM University.Department
+WHERE name = 'Computer Science';
+
+SELECT id, name, department_id, position
+FROM University.Faculty
+WHERE department_id = (
+	SELECT id 
+    FROM University.Department
+    WHERE name = 'Computer Science'
+    )
+ORDER BY 4, 2
+;
+
+EXPLAIN SELECT id, name, department_id, position
+FROM University.Faculty
+WHERE department_id = (
+	SELECT id 
+    FROM University.Department
+    WHERE name = 'Computer Science'
+    )
+ORDER BY 4, 2
+;
+CREATE INDEX idx_department_position_name 
+ON University.Faculty (department_id, position, name);
+
+SHOW INDEXES IN University.Faculty;
+
+
+CREATE INDEX idx_department_position 
+ON University.Faculty (department_id, position);
+
+-- Sorting and Grouping 
+
+-- Registration and Course Tables - Sorting and Grouping by semester and Year
+-- Find the number of students registered in each courses for each semester, ordered by year and semester
+
+SELECT *
+FROM University.Registration;
+
+SELECT *
+FROM University.Course;
+
+SELECT c.name AS course_name,
+r.semester AS semester,
+YEAR(r.reg_datetime) AS year,
+COUNT(r.student_id) AS student_count
+FROM University.Registration r
+JOIN University.Course c
+	ON r.course_id = c.id
+WHERE YEAR(r.reg_datetime) = 2023
+GROUP BY 1, 2, 3
+ORDER BY 3, 2
+;
+
+EXPLAIN SELECT c.name AS course_name,
+r.semester AS semester,
+YEAR(r.reg_datetime) AS year,
+COUNT(r.student_id) AS student_count
+FROM University.Registration r
+JOIN University.Course c
+	ON r.course_id = c.id
+WHERE YEAR(r.reg_datetime) = 2023
+GROUP BY 1, 2, 3
+ORDER BY 3, 2
+;
+
+CREATE INDEX idx_reg_course_date 
+ON University.Registration (course_id, semester, reg_datetime);
+
+-- Coverign Index
+-- Find the grades of all students for a specific course, ordered by exam date
+
+SELECT *
+FROM University.Exam;
+
+SELECT student_id,
+grade,
+exam_date
+FROM University.Exam e
+WHERE course_id = 'CS211'
+ORDER BY exam_date;
+
+EXPLAIN SELECT 
+student_id,
+grade,
+exam_date
+FROM University.Exam e
+WHERE course_id = 'CS211'
+ORDER BY exam_date;
+
+CREATE INDEX idx_course_exam_date_grade_student
+ON University.Exam (course_id, exam_date, grade, student_id);
+
+
+
+-- Stored Procedure
+-- a stored procedure to find the grades for students in a specific course for a given year, ordered by exam date
+SHOW INDEXES IN University.Exam;
+
+SELECT *
+FROM University.Exam;
+
+DROP PROCEDURE IF EXISTS grades_course_year
+
+DELIMITER $$
+CREATE PROCEDURE grades_course_year(
+	p_course_id VARCHAR (10),
+    p_year INT
+)
+BEGIN
+	SELECT student_id, 
+    grade,
+    exam_date
+    FROM Exam
+    WHERE course_id = p_course_id
+    AND YEAR(exam_date) = p_year
+    ORDER BY exam_date;
+END $$
+DELIMITER ;
+
+CALL grades_course_year ('CS411', 2023);
+
+-- Creating Composite index covering the stored procedure
+CREATE INDEX idx_course_exam
+ON University.Exam (course_id, exam_date);
+
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