How to Write a Query to Merge Two Accounts and their Activity Logs into One? [closed]

CREATE TABLE user_rtab (
	user_id int PRIMARY KEY,
	username varchar,
	last_name varchar,
	first_name varchar
);

CREATE TABLE lessonstatus_rtab (
	lesson_id int,
	user_id int,
	accessdate timestamp,
	score double,
);

UPDATE lessonstatus_rtab SET user_id=12 WHERE user_id=7;
DELETE FROM user_rtab WHERE user_id=7;

UPDATE lessonstatus_rtab
SET user_id = 1
WHERE user_id = 2
AND NOT EXISTS
(SELECT *
 FROM lessonstatus_rtab e
 WHERE e.lesson_id = lessonstatus_rtab.lesson_id
 AND user_id = 1)

DELETE FROM lessonstatus_rtab
WHERE user_id = 2