如何根據多個欄位刪除SQL表中的重複項
P粉757556355
P粉757556355 2023-10-20 12:01:14
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我有一張遊戲桌,描述如下:

+---------------+-------------+------+-----+---------+----------------+
| Field         | Type        | Null | Key | Default | Extra          |
+---------------+-------------+------+-----+---------+----------------+
| id            | int(11)     | NO   | PRI | NULL    | auto_increment |
| date          | date        | NO   |     | NULL    |                |
| time          | time        | NO   |     | NULL    |                |
| hometeam_id   | int(11)     | NO   | MUL | NULL    |                |
| awayteam_id   | int(11)     | NO   | MUL | NULL    |                |
| locationcity  | varchar(30) | NO   |     | NULL    |                |
| locationstate | varchar(20) | NO   |     | NULL    |                |
+---------------+-------------+------+-----+---------+----------------+

但是每場比賽在表中的某處都有重複的條目,因為每場比賽都在兩支球隊的賽程表中。是否有一個 SQL 語句可以用來根據相同的日期、時間、hometeam_id、awayteam_id、locationcity 和 locationstate 欄位查看並刪除所有重複?

P粉757556355
P粉757556355

全部回覆(2)
P粉781235689

您可以嘗試這樣的查詢:

DELETE FROM table_name AS t1
WHERE EXISTS (
 SELECT 1 FROM table_name AS t2 
 WHERE t2.date = t1.date 
 AND t2.time = t1.time 
 AND t2.hometeam_id = t1.hometeam_id 
 AND t2.awayteam_id = t1.awayteam_id 
 AND t2.locationcity = t1.locationcity 
 AND t2.id > t1.id )

這將在資料庫中僅保留每個具有最小 ID 的遊戲實例的一個範例。

P粉201448898

您應該能夠執行相關子查詢來刪除資料。尋找所有重複的行並刪除除 id 最小的行之外的所有行。對於 MYSQL,需要使用內部連接(相當於 EXISTS 的功能),如下所示:

delete games from games inner join 
    (select  min(id) minid, date, time,
             hometeam_id, awayteam_id, locationcity, locationstate
     from games 
     group by date, time, hometeam_id, 
              awayteam_id, locationcity, locationstate
     having count(1) > 1) as duplicates
   on (duplicates.date = games.date
   and duplicates.time = games.time
   and duplicates.hometeam_id = games.hometeam_id
   and duplicates.awayteam_id = games.awayteam_id
   and duplicates.locationcity = games.locationcity
   and duplicates.locationstate = games.locationstate
   and duplicates.minid <> games.id)

要進行測試,請將從遊戲中刪除遊戲替換為從遊戲中選擇*。不要只是在資料庫上執行刪除:-)

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