MySQL 如何在 WHERE CLAUSE 中使用 DISTINCT 来避免重复行返回
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How to use DISTINCT in WHERE CLAUSE to avoid repeated row returns
提问by Smiter
The result of this SQL query should return a set of 6 rows.
此 SQL 查询的结果应返回一组 6 行。
SELECT baseFeeds.siteURL, feedFinishes.timeTaken, feedFinishes.timeSubmitted
FROM feedFinishes
LEFT OUTER JOIN baseFeeds
ON feedFinishes.GUID = baseFeeds.GUID
WHERE feedFinishes.nowDate = baseFeeds.nowDate
AND baseFeeds.siteURL LIKE '%www.example.com%'
Currently it returns 18 rows, the correct 6 rows are being repeated 3 times. I figure a solution to this is to have another WHERE clause something similar to:
目前它返回 18 行，正确的 6 行被重复了 3 次。我想一个解决方案是有另一个 WHERE 子句类似于：
WHERE DISTINCT feedFinishes.ID
WHERE DISTINCT feedFinishes.ID
After researching this I have tried:
在研究了这个之后，我尝试过：
SELECT baseFeeds.siteURL, feedFinishes.timeTaken, feedFinishes.timeSubmitted
FROM feedFinishes
JOIN baseFeeds
ON feedFinishes.GUID = baseFeeds.GUID
WHERE baseFeeds.siteURL LIKE '%www.example.com%' AND feedFinishes.ID in
(SELECT ID FROM feedFinishes GROUP BY ID HAVING COUNT(ID)=1);
After the discussion found here
讨论后发现here
Alas, this still returns 18 rows. I believe the answer is similar to here
唉，这仍然返回 18 行。我相信答案类似于这里
Any advice would be appreciated.
任何意见，将不胜感激。
回答by potashin
You should apply group byclause.
你应该申请group by条款。
SELECT
baseFeeds.siteURL, feedFinishes.timeTaken, feedFinishes.timeSubmitted
FROM feedFinishes
JOIN baseFeeds
ON feedFinishes.GUID = baseFeeds.GUID
WHERE baseFeeds.siteURL LIKE '%www.example.com%'
GROUP BY
baseFeeds.siteURL, feedFinishes.timeTaken, feedFinishes.timeSubmitted
