嘗試加入兩個派生表時出錯

Question

我瘋了，試圖找出這個錯誤。 我在MySQL工作，需要在公共列上連接兩個派生表。 兩個表中的所有列都是表格別名。

方案是

stops (id, name)

route (num, company, pos, stop)在哪里

stops.id <---> route.stop

這些表包含城市之間的公交路線，我想弄清楚從'Craiglockhart'到'Sighthill'的所有路線，這些路線只需要兩條公交車（即轉機點）。 此外，因為route表不包含停止名稱（僅ID），我們在派生表中使用一些連接來引用按名稱停止; 這只是一個方便）

所以我試着制作兩個派生表。 其中一條路線可以讓人們在'Craiglockhart'和任何不是'Craighartlock'的車站和一個相同的第二個衍生車牌之間，而是'Sighthill'。 我能夠讓這兩個表單獨工作。

但是，當我試圖沿着所謂的轉運站的公共列（即第一個表中的非Craighartlock站和第二個表中的非Sighthill站）加入它們時，我收到錯誤。

派生表1 ：此工作正常並正確返回表。 這里， stop_b.name表示不是Craiglockhart的轉移站， stop_a.name表示Craighill“起始”站。

SELECT * FROM 
    (SELECT a.num AS num_a, a.company AS comp_a, stop_a.name AS name_a, 
            stop_b.name AS name_transfer FROM
               route a JOIN route b ON (a.company=b.company AND a.num=b.num)
                    JOIN stops stop_a ON (a.stop=stop_a.id)
                    JOIN stops stop_b ON (b.stop=stop_b.id)
                    WHERE stop_a.name = 'Craiglockhart' AND 
                          stop_b.name <> 'Craiglockhart') AS first_route

派生表2 ：相同但不同的表別名和站限制。 這里stop_b.name表示轉移站（不是Sighthill）， stop_a.name表示Sighthill“結束”站。

SELECT * FROM 
    (SELECT a.num AS num_a, a.company AS comp_a, stop_a.name AS name_a, 
            stop_b.name AS name_transfer FROM
               route a JOIN route b ON (a.company=b.company AND a.num=b.num)
                    JOIN stops stop_a ON (a.stop=stop_a.id)
                    JOIN stops stop_b ON (b.stop=stop_b.id)
                    WHERE stop_a.name = 'Sighthill' AND 
                          stop_b.name <> 'Sighthill') AS second_route

但是，當我嘗試將它們連接到它們共同的`name_transfer'列（兩者中的stop_b.name的別名）時，我收到一個錯誤：

SELECT * FROM
(
SELECT * FROM 
    (SELECT a.num AS num_a, a.company AS comp_a, stop_a.name AS name_a, 
            stop_b.name AS name_transfer FROM
               route a JOIN route b ON (a.company=b.company AND a.num=b.num)
                    JOIN stops stop_a ON (a.stop=stop_a.id)
                    JOIN stops stop_b ON (b.stop=stop_b.id)
                    WHERE stop_a.name = 'Craiglockhart' AND 
                          stop_b.name <> 'Craiglockhart') AS first_route
JOIN

(SELECT * FROM 
    (SELECT a.num AS num_a, a.company AS comp_a, stop_a.name AS name_a, 
            stop_b.name AS name_transfer FROM
               route a JOIN route b ON (a.company=b.company AND a.num=b.num)
                    JOIN stops stop_a ON (a.stop=stop_a.id)
                    JOIN stops stop_b ON (b.stop=stop_b.id)
                    WHERE stop_a.name = 'Sighthill' AND 
                          stop_b.name <> 'Sighthill') AS second_route)

ON (first_route.name_transfer = second_route.name_transfer)
)

我也嘗試用USING (name_transfer)替換ON ，因為我要在兩個派生表中調用我想要加入派生表的列。

任何幫助將不勝感激！

Answer 1

在FROM或JOIN子句中使用子查詢時，需要圍繞子查詢使用括號。 您在FROM子句中擁有它，但在JOIN子句中沒有它。 當你在每個子查詢周圍添加不​​必要的SELECT * FROM SELECT時，問題似乎就出現了。

SELECT * FROM 
    (SELECT a.num AS num_a, a.company AS comp_a, stop_a.name AS name_a, 
            stop_b.name AS name_transfer FROM
               route a JOIN route b ON (a.company=b.company AND a.num=b.num)
                    JOIN stops stop_a ON (a.stop=stop_a.id)
                    JOIN stops stop_b ON (b.stop=stop_b.id)
                    WHERE stop_a.name = 'Craiglockhart' AND 
                          stop_b.name <> 'Craiglockhart') AS first_route
JOIN

    (SELECT a.num AS num_a, a.company AS comp_a, stop_a.name AS name_a, 
            stop_b.name AS name_transfer FROM
               route a JOIN route b ON (a.company=b.company AND a.num=b.num)
                    JOIN stops stop_a ON (a.stop=stop_a.id)
                    JOIN stops stop_b ON (b.stop=stop_b.id)
                    WHERE stop_a.name = 'Sighthill' AND 
                          stop_b.name <> 'Sighthill') AS second_route

ON first_route.name_transfer = second_route.name_transfer

Answer 2

試試這個吧。

SELECT * FROM
    (SELECT * FROM 
        (SELECT a.num AS num_a, a.company AS comp_a, stop_a.name AS name_a, 
                stop_b.name AS name_transfer FROM
                   route a JOIN route b ON (a.company=b.company AND a.num=b.num)
                        JOIN stops stop_a ON (a.stop=stop_a.id)
                        JOIN stops stop_b ON (b.stop=stop_b.id)
                        WHERE stop_a.name = 'Craiglockhart' AND 
                              stop_b.name <> 'Craiglockhart') AS first_route) AS A
    JOIN

    (SELECT * FROM 
        (SELECT a.num AS num_a, a.company AS comp_a, stop_a.name AS name_a, 
                stop_b.name AS name_transfer FROM
                   route a JOIN route b ON (a.company=b.company AND a.num=b.num)
                        JOIN stops stop_a ON (a.stop=stop_a.id)
                        JOIN stops stop_b ON (b.stop=stop_b.id)
                        WHERE stop_a.name = 'Sighthill' AND 
                              stop_b.name <> 'Sighthill') AS second_route)B
    ON (A.name_transfer = B.name_transfer)