USE my_tutorial;
SELECT CONCAT('string1', '-', 'string2');
SELECT f_name, l_name , 
CONCAT(f_name, '-',l_name) as name
FROM student_name;

SELECT f_name, l_name , 
CONCAT(COALESCE(f_name,'-'), '-',COALESCE(l_name,'-')) as name
FROM student_name;