选择连接表的行数

Question

我有两个具有一对多关系的表。我通过id列加入表格。我的问题是我需要从第二个（tablekey_id）表中的所有匹配项的计数，但我需要从布尔is_basedomain标记的行中的信息。作为说明，只有一行is_basedomain = 1，每行同一个tablekey_id。

表：tablekey

id linkdata_id timestamp 
22 9495028175 2013-03-10 01:13:46 
23 8392740179 2013-03-10 21:23:25 

表：searched_domains。

注意：tablekey_id是tablekey表中id的外键。

id tablekey_id domain  is_basedomain 
1 22   somesite.com 1 
2 22   yahoo.com  0 
3 23   red.com  1 
4 23   blue.com  0 
5 23   green.com  0 

继承人查询我正在使用。我试图使用子查询，但我似乎不能选择当前tablekey_id的计数，所以这是行不通的。

SELECT `tablekey_id`, `linkdata_id`, `timestamp`, `domain`, `is_basedomain`, 
    (SELECT COUNT(1) AS other FROM `searched_domains` AS dd 
    ON dd.tablekey_id = d.tablekey_id GROUP BY `tablekey_id`) AS count 
FROM `tablekey` AS k 
JOIN `searched_domains` AS d 
ON k.id = d.tablekey_id 
WHERE `is_basedomain` = 1 GROUP BY `tablekey_id` 

，我想找回的是结果：

tablekey_id linkdata_id timestamp   domain  is_basedomain count 
22   9495028175 2013-03-10 01:13:46 somesite.com 1    2 
23   8392740179 2013-03-10 21:23:25 red.com  1    3 

谁能帮助我进入一个查询呢？

Answer 1

你可以把那些is_basedomain = 1，查询中一个单独的表中searched_domains行，并与searched_domains的另一个实例加入它（获取数）：

SELECT 
    d.tablekey_id, 
    k.linkdata_id, 
    k.timestamp, 
    d.domain, 
    d.is_basedomain, 
    COUNT(*) as 'count' 
FROM 
    tablekey AS k 
     join searched_domains AS d on d.tablekey_id=k.id 
     join searched_domains AS d2 on d2.tablekey_id=d.tablekey_id 
WHERE 
    d.is_basedomain = 1 
GROUP BY 
    d.tablekey_id, 
    k.linkdata_id, 
    k.timestamp, 
    d.domain, 
    d.is_basedomain 

Answer 2

您使用ON时改用WHERE

试试这个

SELECT `tablekey_id`, `linkdata_id`, `timestamp`, `domain`, `is_basedomain`, 
    (SELECT COUNT(1) AS other FROM `searched_domains` AS dd 
    where dd.tablekey_id = d.tablekey_id GROUP BY `tablekey_id`) AS count 

    FROM `tablekey` AS k 
    JOIN `searched_domains` AS d 
    ON k.id = d.tablekey_id 
    WHERE `is_basedomain` = 1 GROUP BY `tablekey_id` 

DEMO HERE

Answer 3

没有理由使用子查询，或者您有什么看法有一个错误？

SELECT 
    `tablekey_id`, 
    `linkdata_id`, 
    `timestamp`, 
    `domain`, 
    `is_basedomain`, 
    COUNT(*) as count 
FROM 
    `tablekey` AS k , 
    `searched_domains` AS d 
WHERE 
    k.id = d.tablekey_id AND 
    `is_basedomain` = 1 
GROUP BY 
    `tablekey_id`, 
    `linkdata_id`, 
    `timestamp`, 
    `domain`, 
    `is_basedomain` 

如果你只想要最新的时间戳使用MAX(timestamp) as timestamp和group by删除它。