DELIMITER $$
CREATE PROCEDURE addColumnToTable(IN tbl_name VARCHAR(64), IN col_name VARCHAR(64))
BEGIN
IF ((
SELECT COUNT(*) FROM information_schema.COLUMNS
WHERE TABLE_NAME = tbl_name AND COLUMN_NAME = col_name
)=0) THEN
SET @query = CONCAT('ALTER TABLE ', tbl_name, ' ADD ', col_name, ' varchar(24) NOT NULL DEFAULT "";');
PREPARE stmt FROM @query;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END IF;
END $$
DELIMITER ;