MySQL幫助清理總計數

Question

JOIN語句存在問題。

我試圖讓每名共有，而不是目前的1噸的其他同名記錄

SELECT a.`name`, 
    (SELECT COUNT(b.`id`) 
    FROM `host1_hosting` AS b 
    WHERE b.`id` = c.`host1_servers_host1_hosting_1host1_hosting_idb`) AS HostingCount 
FROM `host1_servers` AS a 
LEFT JOIN `host1_servers_host1_hosting_1_c` AS c ON c.`host1_servers_host1_hosting_1host1_servers_ida` = a.`id` 
ORDER BY a.`name` 

例子返回的

名稱HostingCount

名稱1

名稱1

名稱1

，它應該是：

名稱3

我敢肯定，這是簡單的，但它的早期星期一，我雲裏霧裏

查詢2

SELECT a.`name`, COUNT(d.`id`) 
FROM `host1_servers` AS a 
JOIN `host1_servers_host1_hosting_1_c` AS c ON c.`host1_servers_host1_hosting_1host1_servers_ida` = a.`id` 
JOIN `host1_hosting` AS d ON d.`id` = c.`host1_servers_host1_hosting_1host1_hosting_idb` 
ORDER BY a.`name` 

給我1個名字記錄，但總共爲COUNT

Answer 1

你的第二個查詢需要一個group by：

SELECT a.`name`, COUNT(d.`id`) 
FROM `host1_servers` AS a 
JOIN `host1_servers_host1_hosting_1_c` AS c ON c.`host1_servers_host1_hosting_1host1_servers_ida` = a.`id` 
JOIN `host1_hosting` AS d ON d.`id` = c.`host1_servers_host1_hosting_1host1_hosting_idb` 
GROUP BY a.name 
ORDER BY a.`name`; 

沒有GROUP BY，MySQL的解釋查詢作爲聚合查詢產生一行。總數爲count()。 name這一列是從一行中任意選擇的（使用MySQL擴展，它不適用於任何其他數據庫）。

編輯：

如果你想保留的所有名稱從第一個表，做計數，使用left outer join：

SELECT a.`name`, COUNT(d.`id`) 
FROM `host1_servers` a LEFT OUTER JOIN 
    `host1_servers_host1_hosting_1_c` c 
    ON c.`host1_servers_host1_hosting_1host1_servers_ida` = a.`id` LEFT OUTER JOIN 
    `host1_hosting` d 
    ON d.`id` = c.`host1_servers_host1_hosting_1host1_hosting_idb` 
GROUP BY a.name 
ORDER BY a.`name`;