[英]MySQL Select from multiple tables ordered by count of left joined table
我一直在嘗試從多個表中選擇數據,而我是按照我通過左聯接聯接的另一個表中的ID計數進行排序的。 一切工作都很好,除了計數增加了600左右,而不是每行增加一個。
正如我在類似問題中看到的那樣,我嘗試在count語句中放入不同的內容,但是凍結數據庫的唯一結果是。
表格:
CREATE TABLE IF NOT EXISTS `places` (
`PlaceId` int(10) NOT NULL AUTO_INCREMENT,
`Name` varchar(45) COLLATE utf8_unicode_ci NOT NULL,
`AreaId` int(10) NOT NULL DEFAULT '1',
PRIMARY KEY (`PlaceId`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=0;
CREATE TABLE IF NOT EXISTS `places_descriptions` (
`DescId` int(45) NOT NULL AUTO_INCREMENT,
`PlaceId` int(10) NOT NULL,
`Description` varchar(1024) COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (`DescId`),
KEY `PlaceId` (`PlaceId`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=0;
CREATE TABLE IF NOT EXISTS `places_hits` (
`HitId` int(45) NOT NULL AUTO_INCREMENT,
`PlaceId` int(45) NOT NULL,
PRIMARY KEY (`HitId`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=0;
查詢:
SELECT
p.PlaceId,
p.Name,
pd.Description,
COUNT(ph.HitId) AS numHits
FROM
places_descriptions AS pd,
places AS p
LEFT JOIN places_hits AS ph
ON (p.PlaceId = ph.PlaceId)
WHERE
(p.PlaceId = pd.PlaceId) AND
(p.AreaId = 1)
GROUP BY
p.PlaceId,
p.Name,
pd.Description
ORDER BY
numHits DESC,
p.PlaceId
LIMIT 0, 10
有任何想法嗎? 謝謝!
乍一看,您的問題可能是因為沒有ON子句而使pd和p交叉連接。 where的placeId = placeId通過過濾掉連接不准確的行來掩蓋此問題,但最好將該條件置於ON。 盡管我不確定,但是在過濾之前實際存在的大量行可能會使計數失敗。
試試這個,開始:
SELECT
p.PlaceId,
p.Name,
pd.Description,
COUNT(ph.HitId) AS numHits
FROM
places_descriptions AS pd
INNER JOIN places AS p
ON p.PlaceId = pd.PlaceID
LEFT JOIN places_hits AS ph
ON (p.PlaceId = ph.PlaceId)
WHERE
(p.AreaId = 1)
GROUP BY
p.PlaceId,
p.Name,
pd.Description
ORDER BY
numHits DESC,
p.PlaceId
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