MySQL中刪除重複數據只保留一條

用SQL語句,刪除掉重複項只保留一條

在幾千條記錄裏,存在着些相同的記錄,如何能用SQL語句,刪除掉重複的呢 
一、查找表中多餘的重複記錄，重複記錄是根據單個字段（peopleId）來判斷

  
  
  
  

   
   
   
   
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SELECT * FROM people WHERE peopleId IN ( SELECT peopleId FROM people GROUP BY peopleId HAVINGcount(peopleId) > 1 )

二、刪除表中多餘的重複記錄，重複記錄是根據單個字段（peopleId）來判斷，只留有rowid最小的記錄

  
  
  
  

   
   
   
   
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DELETEFROM people WHERE peopleName IN ( SELECT peopleName FROM people GROUP BY peopleName HAVINGcount(peopleName) > 1 ) AND peopleId NOT IN ( SELECTmin(peopleId) FROM people GROUP BY peopleName HAVINGcount(peopleName) > 1 ) 

三、查找表中多餘的重複記錄（多個字段）

  
  
  
  

   
   
   
   
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SELECT * FROM vitae a WHERE (a.peopleId, a.seq) IN ( SELECT peopleId, seq FROM vitae GROUP BY peopleId, seq HAVINGcount(*) > 1 )

四、刪除表中多餘的重複記錄（多個字段），只留有rowid最小的記錄

  
  
  
  

   
   
   
   
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DELETEFROM vitae a WHERE (a.peopleId, a.seq) IN ( SELECT peopleId, seq FROM vitae GROUP BY peopleId, seq HAVINGcount(*) > 1 ) AND rowid NOT IN ( SELECTmin(rowid) FROM vitae GROUP BY peopleId, seq HAVINGcount(*) > 1 )

五、查找表中多餘的重複記錄（多個字段），不包含rowid最小的記錄

  
  
  
  

   
   
   
   
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SELECT * FROM vitae a WHERE (a.peopleId, a.seq) IN ( SELECT peopleId, seq FROM vitae GROUP BY peopleId, seq HAVINGcount(*) > 1 ) AND rowid NOT IN ( SELECTmin(rowid) FROM vitae GROUP BY peopleId, seq HAVINGcount(*) > 1 )

6.消除一個字段的左邊的第一位：

  
  
  
  

   
   
   
   
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UPDATE tableName SET [ Title ]= RIGHT ([ Title ],(len([ Title ]) - 1)) WHERE Title LIKE '村%'

7.消除一個字段的右邊的第一位：

  
  
  
  

   
   
   
   
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UPDATE tableName SET [ Title ]= LEFT ([ Title ],(len([ Title ]) - 1)) WHERE Title LIKE '%村'

8.假刪除表中多餘的重複記錄（多個字段），不包含rowid最小的記錄

UPDATE vitae SET ispass =- 1WHERE peopleId IN ( SELECT peopleId FROM vitae GROUP BY peopleId

來源：  http://blog.csdn.net/z_youarethebest/article/details/53785435

來自爲知筆記(Wiz)