PostgreSQL: How to efficiently handle many-to-many relationships with composite keys in a join table
I'm relatively new to this, so bear with me... Does anyone know how to After trying multiple solutions online, I still can't figure this out. I'm working on a personal project and I'm working with PostgreSQL 14 and trying to manage a many-to-many relationship between two tables: `students` and `courses`. I've created a join table `student_courses` that includes composite keys from both tables. However, I'm facing performance issues when querying the data, especially when the `student_courses` table grows larger. Here's how my tables are structured: ```sql CREATE TABLE students ( student_id SERIAL PRIMARY KEY, name VARCHAR(100) ); CREATE TABLE courses ( course_id SERIAL PRIMARY KEY, title VARCHAR(100) ); CREATE TABLE student_courses ( student_id INT REFERENCES students(student_id), course_id INT REFERENCES courses(course_id), PRIMARY KEY (student_id, course_id) ); ``` When I try to retrieve all courses for a given student, I'm currently using this query: ```sql SELECT c.title FROM courses c JOIN student_courses sc ON sc.course_id = c.course_id WHERE sc.student_id = $1; -- $1 is the student ID ``` The response time has noticeably increased as the size of `student_courses` has grown. I've created indexes on both `student_id` and `course_id` in the `student_courses` table, but it doesn't seem to have improved performance as expected. I've also tried using a CTE to pre-filter the `student_courses`, but that didn’t yield better results. ```sql WITH student_courses_cte AS ( SELECT course_id FROM student_courses WHERE student_id = $1 ) SELECT c.title FROM courses c JOIN student_courses_cte sc ON sc.course_id = c.course_id; ``` I'm looking for advice on optimizing this query or any best practices for handling large many-to-many relationships in PostgreSQL. Are there specific indexes I should consider or alternative query strategies that could improve performance? Any insights would be greatly appreciated! For context: I'm using Sql on Linux. Any help would be greatly appreciated! I'm working on a CLI tool that needs to handle this. What's the best practice here? I'm working in a Ubuntu 22.04 environment. What am I doing wrong? Any ideas how to fix this? For context: I'm using Sql on Linux. I've been using Sql for about a year now.