Question

查询时这是非法的情况吗？

它返回一个错误，告诉我要检查在votes >= ( SELECT FLOOR((COUNT(*) / (2 + 1)) + 1) threshold FROM votes ) level T附近使用的正确语法。我在MySQL 5.0.83上运行我的数据库。

SELECT CASE WHEN (
SELECT vote_candidate, MAX(votes_above_the_threshold) votes
FROM (
SELECT vote_candidate vote_candidate, COUNT(*) votes_above_the_threshold
FROM vote_orders
WHERE vote_order = 1
GROUP BY vote_candidate
HAVING votes_above_the_threshold >= (
SELECT FLOOR((COUNT(*) / (2 + 1)) + 1) threshold
FROM votes
)
) t
WHERE votes_above_the_threshold = (
SELECT MAX(votes_above_the_threshold)
FROM vote_orders
)
) votes >= (
SELECT FLOOR((COUNT(*) / (2 + 1)) + 1) threshold
FROM votes
) level
THEN (level - original_votes)
ELSE 0
END redistribution

Answer 1

你有几个问题：

您选择两列作为标量子查询 - ＆gt;只选择您感兴趣的那个
您正在提供别名＆＃34;投票＆＃34;对于标量子查询 - ＆gt;删除别名
同样，你有一个＆＃34;等级＆＃34;稍后的标量子查询的别名 - ＆gt;也删除这个

需要注意的是标量子查询只选择一个值而没有别名。

因此，我相信您正在寻找以下内容。请注意评论的差异：

SELECT CASE 
    WHEN (
        SELECT MAX(votes_above_the_threshold) votes
--           ^^^  *NOTE* removed "vote_candidate, "
        FROM (
            SELECT vote_candidate vote_candidate, COUNT(*) votes_above_the_threshold
            FROM vote_orders
            WHERE vote_order = 1
            GROUP BY vote_candidate
            HAVING votes_above_the_threshold >= (
                SELECT FLOOR((COUNT(*) / (2 + 1)) + 1) threshold
                FROM votes
             )
        ) t
        WHERE votes_above_the_threshold = (
            SELECT MAX(votes_above_the_threshold)
            FROM vote_orders
        )
    ) >= (
--   ^^^ *NOTE* removed "votes" alias
        SELECT FLOOR((COUNT(*) / (2 + 1)) + 1) threshold
        FROM votes
    )
--   ^^^ *NOTE* removed "level" alias
THEN (level - original_votes)
ELSE 0
END redistribution

Answer 2

您必须更改此部分：

WHERE votes_above_the_threshold = (
SELECT MAX(votes_above_the_threshold)
FROM vote_orders
)
) votes >= (

到

WHERE votes_above_the_threshold = (
SELECT MAX(votes_above_the_threshold)
FROM vote_orders
)
and votes >= (

这部分错了：

) level
THEN (level - original_votes)
ELSE 0
END redistribution

似乎缺少case when，但我不确定这意味着什么

查询返回语法错误时的MySQL情况

2 个答案: