Add a new column with aggregate query into an existing table in mysql

Question

The two tables are:

1. student (student_id, student_name);

2. score (student_id, subject, score1, score2).

and I want to add a new column to student table to find the average score of all subjects for each student. How can I do that?

Answer 1

Add your score column in students table and then you can update students table with average score like

UPDATE 
  student s 
  JOIN 
    (SELECT 
      student_id,
      AVG(score1 + score2) score 
    FROM
      score 
    GROUP BY student_id) sc 
  ON s.`student_id` = sc.student_id 
SET s.`score` = sc.score