mysql连接两个表，计数和总和别名

Question

我有疑问

SELECT p. * , COUNT( r.poll_option_id ) AS voteCount
FROM poll_options AS p
LEFT JOIN poll_responses AS r ON ( r.poll_option_id = p.id ) 
WHERE p.poll_id =1
GROUP BY p.id
LIMIT 0 , 30

它向我返回了正确的数据

 id poll_id caption voteCount   
 1  1   32  1
 2  1   256 1
 3  1   512 0

现在，我需要计算该别名的票数，因此在本示例中，它将为1 + 1 + 0 = 2。然后将其作为另一个别名返回。 我该怎么办？ 我只能使用1个查询，并且没有编辑数据库的权限。 我已经尝试从MySQL的示例连接两个表的计数和第二个表 MySQL查询的COUNT和SUM，以及两个连接表的COUNT和SUM，还有更多但没有运气。

Answer 1

围绕它包装另一个查询？

SELECT id, poll_id, SUM(voteCount) AS votecount
FROM ( ... your query here ... ) As subquery
GROUP BY poll_id

Answer 2

您可以通过count列的计算总和对您的查询使用交叉联接

SELECT t1.*,t2.totalvoteCount FROM (
SELECT p. * , COUNT( r.poll_option_id ) AS voteCount
FROM poll_options AS p
LEFT JOIN poll_responses AS r ON ( r.poll_option_id = p.id ) 
WHERE p.poll_id =1
GROUP BY p.id
LIMIT 0 , 30
) t1
CROSS JOIN (
SELECT SUM(voteCount) totalvoteCount
FROM (
SELECT  p.id,COUNT( r.poll_option_id ) AS voteCount
FROM poll_options AS p
LEFT JOIN poll_responses AS r ON ( r.poll_option_id = p.id ) 
WHERE p.poll_id =1
GROUP BY p.id
LIMIT 0 , 30
) t
) t2

输出如下

id poll_id caption voteCount   totalvoteCount 
 1  1       32          1        2
 2  1       256         1        2
 3  1       512         0        2

Answer 3

在您的示例中， voteCount代表每个组的计数。 如果要对所有组进行计数，则可以省略group by子句（如果您的选择仅包含一个count ，则这是合法的）。

SELECT COUNT(r.poll_option_id)
FROM poll_options AS p
LEFT JOIN poll_responses AS r ON (r.poll_option_id = p.id)
WHERE p.poll_id =1

要么

SELECT p. * , COUNT( r.poll_option_id ) AS voteCount,
    (SELECT COUNT(r.poll_option_id)
    FROM poll_options AS p
    LEFT JOIN poll_responses AS r ON (r.poll_option_id = p.id)
    WHERE p.poll_id =1) totalVoteCount
FROM poll_options AS p
LEFT JOIN poll_responses AS r ON ( r.poll_option_id = p.id ) 
WHERE p.poll_id =1
GROUP BY p.id
LIMIT 0 , 30