mysql - 如何从表中获取 count_id 和 rating_evarate？

Question

如何从表中获取count_id和rating_evarate？

我想计算 ID 并从下表中获取评分。
我怎样才能在 mysql 中做到这一点。

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- Table structure for `rating`
-- ----------------------------
DROP TABLE IF EXISTS `rating`;
CREATE TABLE `rating` (
  `id` int(11) NOT NULL,
  `rating` int(11) NOT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of rating
-- ----------------------------
INSERT INTO `rating` VALUES ('1', '5');
INSERT INTO `rating` VALUES ('2', '0');
INSERT INTO `rating` VALUES ('3', '0');
INSERT INTO `rating` VALUES ('4', '0');
INSERT INTO `rating` VALUES ('2', '0');
INSERT INTO `rating` VALUES ('1', '0');

Answer 1

你可以试试这个:

SELECT ID
     , COUNT(ID) Count_ID
     , AVG(Rating) AS rating_average
FROM rating
GROUP BY ID;

参见this SQLFiddle