Oracle 尋找與刪除表中重複記錄的步驟方法

這時候如果暫存資料表中有重複資料，無論是主鍵欄位businessid有重複，還是一整行有重複都會報出違反唯一主鍵約束錯誤。

方法：group by XX having count(*)>1,rowid,distinct,temporary table,procedure

1、查詢表中的重複資料
a.重複一個欄位

b.重複多個欄位

c.重複一整行

建立測試表：

複製代碼 代碼如下:create table cfa (businessid number,customer varchar2(50),branchcode varchar2(10),data_date varchar2(10));
insert into cfa values (1,'Albert','SCB','2011-11-11');
insert into cfa values (2,'Andy','DB','2011-11-12');
insert into cfa values (3,'Allen','HSBC','2011-11-13');

---------------以下為重複資料----------------------------------------------
insert into cfa values (1,'Alex','ICBC','2011-11-14');
insert into cfa values (1,'Albert','CTBK','2011-11-15');
insert into cfa values (1,'Albert','SCB','2011-11-11');

對於a的情況,只有businessid重複

複製代碼 代碼如下:select * from cfa where businessid in (select businessid from cfa group by businessid having count(businessid)>1);

如果是b的情況，businessid 和name同時存在重複

複製代碼 代碼如下:select * from cfa where (businessid,customer) in (select businessid,customer from cfa group by businessid,customer having count(*)>1);

對於c的情況，重複一整行

參考b的方法：

複製代碼 代碼如下:select * from cfa where (businessid,customer,branchcode,data_date) in (select * from cfa group by businessid,customer,branchcode,data_date having count(*)>1);

2、刪除表中的重複資料
a情況，刪除表中多餘的重複記錄，重複記錄是根據單個欄位（businessid）來判斷，只留有rowid最小的記錄

也可以只保留rowid不是最小記錄，需要把代碼中的min改為max這裡不再贅述。

複製代碼 代碼如下:delete from cfa
where businessid in (select businessid
from cfa
group by businessid
having count(businessid) > 1)
and rowid not in (select min(rowid)
from cfa
group by businessid
having count(businessid) > 1);

或者，使用下面更簡單高效的語句

複製代碼 代碼如下:DELETE FROM cfa t
WHERE t.ROWID >
(SELECT MIN(X.ROWID) FROM cfa X WHERE X.businessid = t.businessid);

b情況，刪除表中多餘的重複記錄（多個欄位），只留有rowid最小的記錄

複製代碼 代碼如下:delete from cfa
where (businessid,customer) in (select businessid,customer
from cfa
group by businessid,customer
having count(*) > 1)
and rowid not in (select min(rowid)
from cfa
group by businessid,customer
having count(*) > 1);

或者，使用下面更簡單高效的語句

複製代碼 代碼如下:DELETE FROM cfa t
WHERE t.ROWID > (SELECT MIN(X.ROWID)
FROM cfa X
WHERE X.businessid = t.businessid
and x.customer = t.customer);

c情況，這種情況就比較簡單，使用暫存資料表方法

複製代碼 代碼如下:create table cfabak as select distinct * from cfa;

truncate table cfa;--如果是生產最好對該表backup

Insert into cfa select * from cfabak;

commit;