[英]Self Join to find duplicates but including all columns
我想匹配日志表中的任何條目,這些條目發生在同day
, cause
不止一次出現在表中。 我編寫的查詢已經獲取了重復項,我的問題是我需要訪問表中結果中的所有列以供以后的 JOIN 使用。 表看起來像這樣:
| ID | DATE | CAUSE | USER | ... |
|--------------------------------------|
| x | 2017-01-01 | aaa | 100 | ... |
| x | 2017-01-02 | aaa | 101 | ... |
| x | 2017-01-03 | bbb | 101 | ... |
| x | 2017-01-03 | bbb | 101 | ... |
| x | 2017-01-04 | ccc | 101 | ... |
| x | 2017-01-04 | ccc | 101 | ... |
| x | 2017-01-04 | ccc | 101 | ... |
| x | 2017-01-05 | aaa | 101 | ... |
| .....................................|
| .....................................|
| .....................................|
詢問:
SELECT logs.* FROM
(SELECT day, cause FROM logs
GROUP BY day, cause HAVING COUNT(*) > 1) AS logsTwice, logs
WHERE logsTwice.day = logs.day AND logsTwice.cause = logs.cause
子選擇獲取完全正確的數據(日期和原因),但是當我嘗試獲取這些匹配項的附加列時,我得到了完全錯誤的數據。 我究竟做錯了什么?
嘗試這個:
SELECT logs.* FROM logs
inner join
(SELECT day, cause FROM logs GROUP BY day, cause HAVING COUNT(*) > 1) logsTwice
on logsTwice.day = logs.day AND logsTwice.cause = logs.cause
您可以只使用窗口函數:
SELECT l.*
FROM (SELECT l.*,
COUNT(*) OVER (PARTITION BY day, cause) as cnt
FROM logs l
) l
WHERE cnt > 1;
通常,窗口函數將比使用JOIN
和GROUP BY
的等效查詢具有更好的性能。
你可以試試
SELECT l1.*
FROM logs l1
INNER JOIN logs l2
ON (l1.id <> l2.id
AND l1.day = l2.day
AND l1.cause = l2.cause
AND l1.user <> l2.user);
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