MySQL流程控制-while範例

# 字串反轉

DROP FUNCTION `while_ex`;
CREATE DEFINER=`root`@`localhost` FUNCTION `while_ex`(`str` VARCHAR(255)) RETURNS VARCHAR(255) NOT DETERMINISTIC NO SQL SQL SECURITY DEFINER begin
declare _ varchar(255) default '';

while not str is null and str<>'' do
  set _ = concat(_, substr(str, -1,1));
  set str = substr(str,1, length(str)-1);
end while;

return _;
end