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Mysql 如何从表中获取计数id和等级评估?_Mysql_Sql_Count_Average - Fatal编程技术网

Mysql 如何从表中获取计数id和等级评估?

Mysql 如何从表中获取计数id和等级评估?,mysql,sql,count,average,Mysql,Sql,Count,Average,如何从表中获取计数id和等级评估 我想数一数id,并从下面的表格中获得评估等级。 如何在mysql中实现这一点 SET FOREIGN_KEY_CHECKS=0; -- ---------------------------- -- Table structure for `rating` -- ---------------------------- DROP TABLE IF EXISTS `rating`; CREATE TABLE `rating` ( `id` int(11) N

如何从表中获取计数id和等级评估

我想数一数id,并从下面的表格中获得评估等级。
如何在mysql中实现这一点

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');

您可以尝试以下查询:

SELECT id, count_id, AVG(rating_average) FROM rating GROUP BY count_id;
您可以尝试以下方法:

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

请参见您期望输出的最后一个图像?如果是,那么给定的数据是错误的。@mingfish_004-对于给定的数据,您的预期结果是什么?现在我明白了,我想我不明白,看看他的答案。