Question

**更新：标题应该是：Sql Query - 具有最新条目的唯一项目

你好，

我有两张桌子。用户和rsvp 用户具有用户详细信息（id，name，email）
rsvp中有rsvp状态（answerid，userid，eventid，answer）

注意：
回答1 =来回答2 =没有来回答3 =也许
回答4（伪回答）=没有回复

请注意，“回答4”从未出现在实际的rsvp表数据中。它是使用下面的SQL

动态构建的

查看即将到来的人，不是谁，可能会来的人以及没有回复的人的查询如下：

 SELECT
  usrs.name,
  usrs.email,

  (SELECT CASE 
  WHEN rsvp.answer = 1 THEN 'Yes, see you there' 
  WHEN rsvp.answer = 2 THEN 'Cannot make it' 
  WHEN rsvp.answer = 4 THEN 'Cannot make it' 
  WHEN rsvp.answer = 3 THEN 'Maybe'
  ELSE 'No Reply' END) as attendance,

  (SELECT CASE 
  WHEN rsvp.answer = 1 THEN "1" 
  WHEN rsvp.answer = 2 THEN "3"
  WHEN rsvp.answer = 4 THEN "4"
  WHEN rsvp.answer = 3 THEN "2"
  ELSE "5" END) as ordering

  FROM jos_users usrs
  LEFT JOIN jos_rsvp as rsvp on usrs.id = rsvp.userid
  WHERE usrs.id NOT IN (62,63,128)
  ORDER BY ordering

同一位用户可能会多次回复。即首先他们回答是，然后他们改变主意并回复NO。

未更新rsvp答案，只需为新答案插入新记录。上面的SQL的问题在于它不考虑这种重复。

我正在试图找出如何更改它，以便只在结果中显示每个用户的最后一个答案。起初看起来很简单，但现在我无法弄明白。

使用MySQL。

请帮助，
失去的头发
N4〜

Answer 1

这个怎么样？

 SELECT
  usrs.name,
  usrs.email,

  (SELECT CASE 
  WHEN rsvp.answer = 1 THEN 'Yes, see you there' 
  WHEN rsvp.answer = 2 THEN 'Cannot make it' 
  WHEN rsvp.answer = 4 THEN 'Cannot make it' 
  WHEN rsvp.answer = 3 THEN 'Maybe'
  ELSE 'No Reply' END) as attendance,

  (SELECT CASE 
  WHEN rsvp.answer = 1 THEN "1" 
  WHEN rsvp.answer = 2 THEN "3"
  WHEN rsvp.answer = 4 THEN "4"
  WHEN rsvp.answer = 3 THEN "2"
  ELSE "5" END) as ordering

  FROM jos_users usrs, jos_rsvp rsvp,
  (SELECT userid, max(answerid) AS latest_answerid
   FROM jos_rsvp
   WHERE userid NOT IN (62,63,128)
   GROUP BY userid
  ) AS latest_rsvp
  WHERE usrs.id = rsvp.userid
  AND rsvp.userid = latest_rsvp.userid
  AND rsvp.answerid = latest_rsvp.latest_answerid
  ORDER BY ordering

Sql Query - 具有最新日期的唯一项目

1 个答案: