mysql中如何输出变量的值

SET @myVariable = 'Hello, World!';
SELECT @myVariable;

DELIMITER //

CREATE PROCEDURE OutputVariable()
BEGIN
    DECLARE myVariable VARCHAR(255);
    SET myVariable = 'Hello, World!';
    SELECT myVariable;
END //

DELIMITER ;

CALL OutputVariable();

SHOW VARIABLES LIKE 'version';

SET SESSION mySessionVariable = 'Hello, Session!';
SELECT @mySessionVariable;

SET @myVariable = 'Hello, World!';
SELECT @myVariable;

DELIMITER //

CREATE PROCEDURE OutputVariable()
BEGIN
    DECLARE myVariable VARCHAR(255);
    SET myVariable = 'Hello, World!';
    SELECT myVariable;
END //

DELIMITER ;

CALL OutputVariable();

SET @my_Variable = 'Hello, World!';
SELECT @my_Variable;