我已经扫描了StackOverflow和互联网以回答以下问题，但我发现的答案都不适用于我。这是我的问题。
我想通过UNION使用两个查询。我设法将它们按预期结合起来，但我无法按照我想要的方式对它们进行分组。我希望通过对子查询进行排序来隐藏重新分配值为0的重复行，以便在分组时对它们进行优先级排序...（我知道错误的解释 - 我希望下面的图形演示更好地解释它。我要删除的行在右边缘标有一个小箭头。）
我该如何做到这一点？
+-----------+-------+---------------+----------------+----------------------------+
| CANDIDATE | VOTES | RANKED_CHOICE | REDISTRIBUTION | VOTES_AFTER_REDISTRIBUTION |
+-----------+-------+---------------+----------------+----------------------------+
| 1 | 8 | 0 | 0 | 8 |
| 2 | 1 | 6 | -1 | 0 |
| 2 | 1 | 0 | 0 | 1 | >
| 3 | 2 | 0 | 0 | 2 |
| 4 | 4 | 0 | 0 | 4 |
| 5 | 2 | 0 | 0 | 2 |
| 6 | 3 | 0 | 0 | 3 | >
| 6 | 3 | 0 | 1 | 4 |
+-----------+-------+---------------+----------------+----------------------------+
-- The resulting table that's shown on the screen
SELECT vote_candidate candidate, original_votes votes, ranked_choice, redistribution, (original_votes + redistribution) votes_after_redistribution
FROM (
-- Create the first table with original information
SELECT c.vote_candidate, c.original_votes, '0' ranked_choice, '0' redistribution
FROM (
SELECT o.vote_candidate, COUNT(*) original_votes
FROM vote_orders o
WHERE o.vote_order = 1
GROUP BY o.vote_candidate
) c
GROUP BY c.vote_candidate
-- Union a second table containing the second ranked choice of an eliminated candidate and the redistribution.
-- This is done in two steps. In the first step we find out the ranking. In the second step we union the ranked
-- candidate and its' redistribution with each other
UNION
SELECT vote_candidate, original_votes, ranked_choice, redistribution
FROM ((
SELECT vote_candidate, IFNULL(d.original_votes, 0) original_votes, IFNULL(COUNT(*), 0) ranked_choice, (0 - IFNULL(d.original_votes, 0)) redistribution
FROM vote_orders a
-- Get the second favored vote from each eliminated candidates ballots
INNER JOIN (
SELECT vote_id, c, MIN(minimum_vote)
FROM (
SELECT vote_id, vote_candidate c, COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t1
WHERE minimum_vote = (
SELECT MIN(minimum_vote)
FROM (
SELECT COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t2
)
GROUP BY c
) b
ON a.vote_id = b.vote_id
-- Get the eliminated candidates votes at the beginning of this round
LEFT OUTER JOIN
(
SELECT vote_candidate o, COUNT(*) original_votes
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) d
ON a.vote_candidate = d.o
GROUP BY vote_candidate
ORDER BY redistribution DESC
LIMIT 1
-- Union the candidates redistribution
UNION
(
SELECT vote_candidate, d.original_votes, '0' ranked_choice, (CASE
WHEN IFNULL(d.original_votes, 0) = 0
THEN (0 - IFNULL(d.original_votes, 0))
ELSE (
SELECT MIN(minimum_vote)
FROM (
SELECT vote_candidate c, COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t1
WHERE minimum_vote = (
SELECT MIN(minimum_vote)
FROM (
SELECT COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t2
)
GROUP BY c
)
END) redistribution
FROM vote_orders a
INNER JOIN (
SELECT vote_id, MIN(minimum_vote)
FROM (
SELECT vote_id, COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t1
WHERE minimum_vote = (
SELECT MIN(minimum_vote)
FROM (
SELECT COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t2
)
) b
ON a.vote_id = b.vote_id
LEFT OUTER JOIN
(
SELECT vote_candidate o, COUNT(*) original_votes
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) d
ON a.vote_candidate = d.o
-- Determine which candidate to add the redistribution to
WHERE vote_candidate = (
SELECT IFNULL(COUNT(*), 0) ranked_choice
FROM vote_orders a
INNER JOIN (
SELECT vote_id, c, MIN(minimum_vote)
FROM (
SELECT vote_id, vote_candidate c, COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t1
WHERE minimum_vote = (
SELECT MIN(minimum_vote)
FROM (
SELECT COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t2
)
GROUP BY c
) b
ON a.vote_id = b.vote_id
)
GROUP BY vote_candidate
ORDER BY redistribution DESC
LIMIT 1
)
)) y
) z
-- This is where the grouping fails on me
-- GROUP BY vote_candidate
ORDER BY vote_candidate ASC;
这是架构：
CREATE TABLE votes
(
vote_id INT NOT NULL AUTO_INCREMENT,
vote_candidate_a INT,
vote_candidate_b INT,
vote_candidate_c INT,
vote_candidate_d INT,
vote_candidate_e INT,
vote_candidate_f INT,
PRIMARY KEY vote_id(vote_id)
);
INSERT INTO votes
VALUES
(NULL, 1, 3, 2, 5, 4, 6),
(NULL, 1, 2, 4, 6, 3, 5),
(NULL, 5, 3, 2, 1, 4, 6),
(NULL, 6, 1, 5, 3, 4, 2),
(NULL, 2, 3, 5, 6, 1, 4),
(NULL, 4, 1, 6, 3, 2, 5),
(NULL, 3, 2, 6, 1, 5, 4),
(NULL, 4, 3, 1, 6, 2, 5),
(NULL, 1, 2, 4, 3, 6, 5),
(NULL, 1, 5, 3, 2, 4, 6),
(NULL, 4, 5, 6, 2, 3, 1),
(NULL, 1, 4, 2, 3, 5, 6),
(NULL, 1, 2, 3, 4, 5, 6),
(NULL, 3, 6, 5, 1, 4, 2),
(NULL, 1, 2, 3, 4, 5, 6),
(NULL, 6, 5, 4, 3, 2, 1),
(NULL, 4, 3, 1, 5, 6, 2),
(NULL, 6, 3, 1, 2, 5, 4),
(NULL, 1, 4, 6, 3, 2, 5),
(NULL, 5, 3, 6, 4, 2, 1);
CREATE TABLE vote_orders
(
id INT NOT NULL AUTO_INCREMENT,
vote_id INT,
vote_order INT,
vote_candidate INT,
PRIMARY KEY id(id)
);
INSERT INTO vote_orders (id, vote_id, vote_order, vote_candidate)
SELECT NULL, vote_id, 1, vote_candidate_a FROM votes
UNION
SELECT NULL, vote_id, 2, vote_candidate_b FROM votes
UNION
SELECT NULL, vote_id, 3, vote_candidate_c FROM votes
UNION
SELECT NULL, vote_id, 4, vote_candidate_d FROM votes
UNION
SELECT NULL, vote_id, 5, vote_candidate_e FROM votes
UNION
SELECT NULL, vote_id, 6, vote_candidate_f FROM votes;
答案 0 :(得分：1)
实际上，你已经知道了vote_candidate和投票数是多少。这是一个简单的查询，
Select vote_candidate, count(*)
From vote_orders
Where vote_order = 1
Group by vote_candidate
这是整个查询的基础，因为select中缺少的唯一内容是ranking_choice，redistribution和votes_after_redistribution（尽管这是非常微不足道的，因为它是来自另外两列的计算）。所以，我建议你使用你所做的所有工作来找到两个缺失的列。基本上，您应该将查询更改为子选择，以仅查找缺少的列。
我将子选择更改为仅查找ranking_choice和再分配值（如果它们不是0）。然后，我抓住这些值（使用左外连接）。如果子选择中没有任何内容，那么我们将该值默认为0。
您之前的查询是通过将所有值默认为0开始，然后返回非0行的信息。让我们跳过所有额外的工作。注意，我仍然建议清理子选择，特别是因为我删除了原始投票的数量。由于您不再需要查找该信息，因此某些连接可能是额外的。小提琴：http://sqlfiddle.com/#!2/1b0cb/51
-- The resulting table that's shown on the screen
SELECT v.vote_candidate candidate,
count(*) votes,
IfNull(z.ranked_choice, 0) ranked_choice,
IfNull(z.redistribution, 0) redistribution,
(count(*) + IfNull(z.redistribution, 0)) votes_after_redistribution
FROM vote_orders v left outer join
(
-- Union a second table containing the second ranked choice of an eliminated candidate and the redistribution.
-- This is done in two steps. In the first step we find out the ranking. In the second step we union the ranked
-- candidate and its' redistribution with each other
SELECT vote_candidate, ranked_choice, redistribution
FROM ((
SELECT vote_candidate,
IFNULL(COUNT(*), 0) ranked_choice,
(0 - IFNULL(d.original_votes, 0)) redistribution
FROM vote_orders a
-- Get the second favored vote from each eliminated candidates ballots
INNER JOIN (
SELECT vote_id, vote_candidate c, MIN(minimum_vote)
FROM (
SELECT vote_id, vote_candidate, COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t2
) b
ON a.vote_id = b.vote_id
-- Get the eliminated candidates votes at the beginning of this round
LEFT OUTER JOIN
(
SELECT vote_candidate o, COUNT(*) original_votes
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) d
ON a.vote_candidate = d.o
GROUP BY vote_candidate
ORDER BY redistribution DESC
LIMIT 1
-- Union the candidates redistribution
UNION
(
SELECT vote_candidate,
0 ranked_choice,
(CASE
WHEN IFNULL(d.original_votes, 0) = 0
THEN (0 - IFNULL(d.original_votes, 0))
ELSE (
SELECT MIN(minimum_vote)
FROM (
SELECT COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t2
)
END) redistribution
FROM vote_orders a
INNER JOIN (
SELECT vote_id, MIN(minimum_vote)
FROM (
SELECT vote_id, COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t1
WHERE minimum_vote = (
SELECT MIN(minimum_vote)
FROM (
SELECT COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t2
)
) b
ON a.vote_id = b.vote_id
LEFT OUTER JOIN
(
SELECT vote_candidate o, COUNT(*) original_votes
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) d
ON a.vote_candidate = d.o
-- Determine which candidate to add the redistribution to
WHERE vote_candidate = (
SELECT IFNULL(COUNT(*), 0) ranked_choice
FROM vote_orders a
INNER JOIN (
SELECT vote_id, c, MIN(minimum_vote)
FROM (
SELECT vote_id, vote_candidate c, COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t1
WHERE minimum_vote = (
SELECT MIN(minimum_vote)
FROM (
SELECT COUNT(*) minimum_vote
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
) t2
)
GROUP BY c
) b
ON a.vote_id = b.vote_id
)
GROUP BY vote_candidate
ORDER BY redistribution DESC
LIMIT 1
)
)) y
) z
on v.vote_candidate = z.vote_candidate
Where v.vote_order = 1
GROUP BY v.vote_candidate
ORDER BY v.vote_candidate ASC;