如何使用条件计数器获取数据Mysql Group by

Question

Mysql按计数器分组（有多少条件）

嗨，每个人

我想；

• question_id 1和答案2
• question_id 2和答案2
• question_id 3和ve回答2
• question_id 4和ve回答2
• question_id 5和ve回答2

我想按object_id分组，看看在一个名为match_number的字段中有多少条件与object_id相匹配。

喜欢结果；

Object_id   Eşleşme_sayısı
    1             3
    2             5

筛选表格；

表中的sql代码；

CREATE TABLE `object_answers` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `question_id` int(11) unsigned DEFAULT NULL,
  `object_id` int(11) unsigned DEFAULT NULL,
  `answer` int(2) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `object_answers_question_id_foreign` (`question_id`),
  KEY `object_answers_object_id_foreign` (`object_id`),
  CONSTRAINT `object_answers_object_id_foreign` FOREIGN KEY (`object_id`) REFERENCES `object` (`id`) ON DELETE CASCADE,
  CONSTRAINT `object_answers_question_id_foreign` FOREIGN KEY (`question_id`) REFERENCES `question` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=51 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

CREATE TABLE `object_answers` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `question_id` int(11) unsigned DEFAULT NULL,
  `object_id` int(11) unsigned DEFAULT NULL,
  `answer` int(2) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `object_answers_question_id_foreign` (`question_id`),
  KEY `object_answers_object_id_foreign` (`object_id`),
  CONSTRAINT `object_answers_object_id_foreign` FOREIGN KEY (`object_id`) REFERENCES `object` (`id`) ON DELETE CASCADE,
  CONSTRAINT `object_answers_question_id_foreign` FOREIGN KEY (`question_id`) REFERENCES `question` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=51 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

Answer 1

您可以使用MySQL在数字上下文中将布尔表达式转换为0或1的功能。因此，您可以间接求和布尔表达式。

SELECT obejct_id,
       sum(question_id IN (1, 2, 3, 4, 5)
           AND answer = 2) "Eşleşme_sayısı"
       FROM object_answers
       GROUP BY object_id;