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Question

获取错误消息[错误] 1060 - 重复列名'id'

SELECT c.id, c.name, COUNT(all.id) 'All', 
       COUNT(unanswered.id) 'Unanswered',
       COUNT(unchecked.id) 'Unchecked'
FROM courses c
INNER JOIN courses-lessons cl ON c.id = cl.cid
INNER JOIN questions all ON cl.id = all.lid
INNER JOIN
(
    SELECT * 
    FROM questions
    WHERE id NOT IN (SELECT qid FROM answers)
) unanswered ON cl.id = unchecked.lid
INNER JOIN
(
    SELECT *
    FROM questions q
    INNER JOIN 
    (
        SELECT * 
        FROM answers
        WHERE id NOT IN (SELECT aid FROM answer_chk_results)
    ) a ON q.id = a.qid 
) unchecked ON cl.id = unchecked.lid
GROUP BY c.id, c.name

我错过了什么？找不到什么错误。

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数据库结构

https://docs.google.com/open?id=0B9ExyO6ktYcOenZ1WlBwdlY2R3c

Answer 1

您的问题和答案表都有id列。当你做SELECT *时，你会得到两个id列。尝试在SELECT中指定所需的列，而不是使用*

请点击此处查看类似问题：SQL Duplicate column name error

Answer 2

不确定问题是否属于您的问题，但您不应将表别名为“all”，因为它是MySQL关键字。

Answer 3

这很可能是你的查询的这一部分：

SELECT *
FROM questions q
INNER JOIN 
(
    SELECT * 
    FROM answers
    WHERE id NOT IN (SELECT aid FROM answer_chk_results)
) a ON q.id = a.qid

外部查询将有两个名为id的字段，您应该指定所需的id字段。此外，您应该调出所需的字段，而不是使用SELECT *。

ALL也是reserved word，我会考虑更改别名或在其周围使用反引号`。

根据您的表格结构，它看起来像你想要的那样：

SELECT c.id, 
    c.name, 
    COUNT(allq.id) 'All', 
    COUNT(unanswered.id) 'Unanswered',
    COUNT(unchecked.id) 'Unchecked'
FROM courses c
INNER JOIN courses-lessons cl 
    ON c.id = cl.cid
INNER JOIN questions allq 
    ON cl.id = allq.lid
INNER JOIN
(
    SELECT q.id, a.qid, q.lid
    FROM questions q
    INNER JOIN 
    (
        SELECT id, qid
        FROM answers
        WHERE id NOT IN (SELECT aid FROM answer_chk_results)
    ) a 
        ON q.id = a.qid 
) unchecked 
    ON cl.id = unchecked.lid
INNER JOIN
(
    SELECT id
    FROM questions
    WHERE id NOT IN (SELECT qid FROM answers)
) unanswered 
    ON cl.id = unchecked.lid
GROUP BY c.id, c.name

有MySQL语句的问题

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3 个答案: