Question

我正在构建一个轮询系统，我现在有一个查询，它应该选择所有的民意调查并计算每个民意调查的所有选票（位于一个单独的表格中）。所以我的表看起来像：

Polls:  
ID  
Title  
Body

Votes:  
ID  
PollID  
Vote  (This value is either 0 or 1)

总票数看起来好像有效，问题是它目前只显示一条记录。

目前我的查询如下：

SELECT POLLS.ID, 
       POLLS.TITLE, 
       POLLS.BODY, 
       Sum(CASE 
             WHEN VOTES.VOTE = 1 
                  AND VOTES.POLLID = POLLS.ID THEN 1 
             ELSE 0 
           END) AS yay, 
       Sum(CASE 
             WHEN VOTES.VOTE = 0 
                  AND VOTES.POLLID = POLLS.ID THEN 1 
             ELSE 0 
           END) AS nay, 
       FROM     polls, 
       VOTES 
ORDER  BY POLLS.ID

我也在使用PHP和Codeigniter。

Answer 1

SELECT polls.ID,polls.title,polls.body,
  SUM(case when votes.vote = 1 then 1 else 0 end) AS yay,
  SUM(case when votes.vote = 0 then 1 else 0 end) AS nay,
FROM polls 
JOIN votes ON polls.ID = votes.pollID
  GROUP BY poll.ID, polls.title, polls.body
  ORDER BY polls.ID

Answer 2

您需要GROUP BY pollID votes表格中的SELECT p.ID, p.title, p.body, v.yay, v.nay FROM ( SELECT PollID, SUM(CASE WHEN vote = 1 THEN 1 ELSE 0 END) AS yay, SUM(CASE WHEN vote = 0 THEN 1 ELSE 0 END) AS nay, FROM votes GROUP BY PollID ) v INNER JOIN Polls p ON v.PollID = p.Id ORDER BY p.ID值：

{{1}}

Answer 3

我会选择：

    SELECT polls.ID, polls.title, polls.body,
    SUM(IF(votes.vote = 1, 1, 0)) AS yay, 
    SUM(IF(votes.vote = 0, 1, 0)) AS nay
    FROM polls
    JOIN votes ON (votes.pollID = polls.ID)
    GROUP BY ID, title, body

Answer 4

您缺少的是“GROUP BY”。在获取总和时使用GROUP BY PollID。

一起查询两个表，只显示一个记录

4 个答案: