如何按日期和ID删除MySQL表上的重复项？

Question

我有一张表格，其结果来自应用。 一些结果是重复的，我可以看到哪个“survey_question_id”有重复的答案。

通过此查询，我可以看到每个“survey_question_id”有多少重复：

    SELECT `id`,`survey_question_id`,
   `question`,`date`, COUNT(*) 
   FROM answers 
   GROUP BY `survey_question_id`, `date` 
   HAVING COUNT(*) > 1 and `date` > '2015-10-15'

表格结果：

如何删除重复项？

Answer 1

你可以

1. 创建表your_table2作为select original * from original_table 然后只是
2. 使用一些级联约束和
删除original_table
3. 更改your_table2，重命名并添加所有约束 或只是删除original_table中的所有数据，只需插入original_table select * from your_table2

我认为this与您的问题类似。

Answer 2

试试这个：

DELETE FROM answers
WHERE date > '2015-10-15'
AND id NOT IN 
  (SELECT id
      FROM (SELECT MIN(id) AS id  FROM answers
            WHERE date > '2015-10-15'
            GROUP BY survey_question_id) x
  )

Answer 3

删除重复记录时，您可以使用：

如果你想保持最低ID，你可以使用它：

deg.arr <- c(atan2(y.arr, exp(x.arr)), NA)
theta <- atan2((y2 - y1) * uin[2], exp((x2 - x1)) * uin[1])

如果你想保留HIGEST id，你可以使用它：

DELETE n1 FROM answers n1, answers n2 WHERE n1.id > n2.id 
AND n1.id <> n2.id
AND n1.survey_question_id = n2.survey_question_id 
AND n1.question = n2.question 
AND n1.date = n2.date

如果您认为以后再次发生这种情况，请添加 UNIQUE INDEX 。

DELETE n1 FROM answers n1, answers n2 WHERE n1.id < n2.id 
AND n1.id <> n2.id
AND n1.survey_question_id = n2.survey_question_id 
AND n1.question = n2.question 
AND n1.date = n2.date

旁注：在执行任何批量删除之前，请确保您拥有此表的副本。