mysql怎么写函数

DELIMITER //

CREATE FUNCTION function_name (parameter_list)
RETURNS data_type
DETERMINISTIC
BEGIN
    -- 函数体
    DECLARE variable_name datatype;
    -- ... 执行 SQL 语句 ...
    RETURN result;
END //

DELIMITER ;

DELIMITER //

CREATE FUNCTION calculate_salary_increase(emp_id INT)
RETURNS DECIMAL(10, 2)
DETERMINistic
BEGIN
    DECLARE new_salary DECIMAL(10, 2);
    SELECT salary * 1.1 INTO new_salary FROM employees WHERE id = emp_id;
    RETURN new_salary;
END //

DELIMITER ;

SELECT calculate_salary_increase(1) AS new_salary;

SHOW FUNCTION STATUS LIKE 'function_name';

GRANT EXECUTE ON FUNCTION function_name TO 'username'@'host';