MariaDB: SP:FUNCITON

CREATE [OR REPLACE]
    [DEFINER = {user | CURRENT_USER | role | CURRENT_ROLE }]
    [AGGREGATE] FUNCTION [IF NOT EXISTS] func_name ([func_parameter[,...]])
    RETURNS type
    [characteristic ...]
    RETURN func_body


func_parameter:
    param_name type


type:
    Any valid MariaDB data type


characteristic:
    LANGUAGE SQL
  | [NOT] DETERMINISTIC
  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
  | COMMENT 'string'


CREATE FUNCTION users_count() RETURNS BOOL
   READS SQL DATA
BEGIN
   RETURN (SELECT COUNT(DISTINCT User) FROM mysql.user);
END;


CREATE FUNCTION max_salary (dept TINYTEXT) RETURNS INT RETURN
  (SELECT MAX(salary) FROM employees WHERE employees.dept = dept);
GRANT EXECUTE ON FUNCTION max_salary TO roger;

CREATE FUNCTION hello (s CHAR(20))
    RETURNS CHAR(50) DETERMINISTIC
    RETURN CONCAT('Hello, ',s,'!');

SELECT hello('world');



CREATE FUNCTION counter () RETURNS INT
  BEGIN
    UPDATE counter SET c = c + 1;
    RETURN (SELECT c FROM counter LIMIT 1);
  END //


CREATE FUNCTION hello2 (s CHAR(20))
  RETURNS CHAR(50) CHARACTER SET 'utf8' COLLATE 'utf8_bin' DETERMINISTIC
  RETURN CONCAT('Hello, ',s,'!');