MySQL 8.0

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CREATE TABLE user_profile (
  profileId INT(11) NOT NULL AUTO_INCREMENT, 
  profile_pic VARCHAR(200) DEFAULT 'profile.png', 
  cover_pic VARCHAR(200), 
  CONSTRAINT pk_profileId PRIMARY KEY(profileId)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
CREATE TRIGGER insert_cover_pic BEFORE INSERT ON user_profile
  FOR EACH ROW 
    SET NEW.cover_pic = IF(NEW.cover_pic IS NULL, ELT(FLOOR(RAND()*2)+1, 'pic1', 'pic2'), NEW.cover_pic);
INSERT INTO user_profile (profile_pic) VALUES
  ('test.png'),
  ('test.png'),
  ('test.png'),
  ('test.png'),
  ('test.png');
INSERT INTO user_profile (profile_pic, cover_pic) VALUES 
  ('test.png', 'own.png');
SELECT * 
FROM user_profile;


profileId
profile_pic
cover_pic


1
test.png
pic2

2
test.png
pic2

3
test.png
pic1

4
test.png
pic1

5
test.png
pic2

6
test.png
own.png

profileId	profile_pic	cover_pic
1	test.png	pic2
2	test.png	pic2
3	test.png	pic1
4	test.png	pic1
5	test.png	pic2
6	test.png	own.png