我需要这段代码来创建一个列，然后使它成为另一个外键。
我不想另一个代码，我需要这是出于某些原因。如何添加代码来修改已创建的列并使其成为外键？

-- Actualizando la tabla: action

DELIMITER $$
SET @s = (SELECT IF(
(SELECT COUNT(*)
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'action'
AND table_schema = 'ibexsales_dev'
AND column_name = 'company_id'
) > 0,
"SELECT 1",
"ALTER TABLE action ADD company_id INT(11) NOT NULL"
));
PREPARE stmt FROM @s;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
$$ DELIMITER ;

我需要添加以下代码：

ALTER TABLE `ibexsales_dev`.`action` 
                    ADD CONSTRAINT `fk_company_id_action` 
                    FOREIGN KEY (`company_id`) REFERENCES company(`company_id`);

我试过了，但没用：

) > 0,
"SELECT 1",
"ALTER TABLE action ADD company_id INT(11) NOT NULL",
"    ALTER TABLE `ibexsales_dev`.`action` 
                    ADD CONSTRAINT `fk_company_id_action` 
                    FOREIGN KEY (`company_id`) REFERENCES company(`company_id`); "
));