Illegal mix of collations for operation 'UNION' Nodejs Mysql - mysql

Question

I´m trying to get all the posts that a user wrote using this sql:
'SELECT * FROM users WHERE username=? UNION ALL SELECT * FROM posts WHERE writer_name=?'
And i´m getting this error:
"Illegal mix of collations for operation 'UNION'"
tables
CREATE TABLE `claudioBlog`.`users` (
`id` INT UNSIGNED NOT NULL AUTO_INCREMENT ,
`username` VARCHAR(100) NOT NULL ,
`email` VARCHAR(100) NOT NULL ,
`age` VARCHAR(100),
`discription` VARCHAR (255),
`ocupation` VARCHAR (100),
`profile_image` VARCHAR (100)
`password` VARCHAR(255) NOT NULL ,
PRIMARY KEY (`id`), UNIQUE (`email`)
) ENGINE = InnoDB
CREATE TABLE posts (
id int(11) NOT NULL AUTO_INCREMENT,
title VARCHAR(50) NOT NULL,
category VARCHAR(50) NOT NULL,
body VARCHAR(2000) NOT NULL,
writer_id VARCHAR(50) NOT NULL,
writer_name VARCHAR(50) NOT NULL,
post_img VARCHAR(100),
created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (id)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
What do i have to chage?

Answer 1

You want a join, not union. Presumably, writer_id is a foreign key reference to users(id)
SELECT p.*
FROM users u JOIN
posts p
ON p.writer_id = u.id
WHERE u.username = ? ;
Note: If write_id does indeed refer to users(id), it is inappropriate to store write_name in posts, unless -- for some strange reason -- it can vary by post and is not the users real name.