mysql into outfile with headers dynamically code example

Example: mysql into outfile with headers

SELECT * FROM (
    SELECT 'username','email'
    UNION ALL
    (
        SELECT `username`,`email`,`steam_id` FROM `users` WHERE `userna` LIKE '%@temp%'
    )
) resulting_set
INTO OUTFILE '/results/result.txt' FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' LINES TERMINATED BY '\n';