Oracle查詢重複資料與刪除重複記錄方法

47328983發表於2013-05-24

 比如現在有一人員表 (表名:peosons)

  若想將姓名、身份證號、住址這三個欄位完全相同的記錄查詢出來

  select p1.*

  from persons p1,persons p2

  where p1.id<>p2.id

  and p1.cardid = p2.cardid and p1.pname = p2.pname and p1.address = p2.address

  可以實現上述效果。

  幾個刪除重複記錄的SQL語句

  1.用rowid方法

  2.用group by方法

  3.用distinct方法

  1。用rowid方法

  據據oracle帶的rowid屬性,進行判斷,是否存在重複,語句如下:

  查資料:

  select * from table1 a where rowid !=(select max(rowid)

  from table1 b where a.name1=b.name1 and a.name2=b.name2……)

  刪資料:

  delete from table1 a where rowid !=(select max(rowid)

  from table1 b where a.name1=b.name1 and a.name2=b.name2……)

  2.group by方法

  查資料:

  select count(num), max(name) from student --列出重複的記錄數,並列出他的name屬性

  group by num

  having count(num) >1 --按num分組後找出表中num列重複,即出現次數大於一次

  刪資料:

  delete from student

  group by num

  having count(num) >1

  這樣的話就把所有重複的都刪除了。

  3.用distinct方法 -對於小的表比較有用

  create table table_new as select distinct * from table1 minux

  truncate table table1;

  insert into table1 select * from table_new;

  查詢及刪除重複記錄的方法大全

  1、查詢表中多餘的重複記錄,重複記錄是根據單個欄位(peopleId)來判斷

  select * from people

  where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)

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

  delete from people

  where peopleId in (select peopleId from people group by peopleId

  having count(peopleId) > 1)

  and rowid not in (select min(rowid) from people group by peopleId having count(peopleId )>1)

  3、查詢表中多餘的重複記錄(多個欄位)

  select * from vitae a

  where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

  4、刪除表中多餘的重複記錄(多個欄位),只留有rowid最小的記錄

  delete from vitae a

  where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

  and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

  5、查詢表中多餘的重複記錄(多個欄位),不包含rowid最小的記錄

  select * from vitae a

  where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

  and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

  (二)

  比方說

  在A表中存在一個欄位“name”,

  而且不同記錄之間的“name”值有可能會相同,

  現在就是需要查詢出在該表中的各記錄之間,“name”值存在重複的項;

  Select Name,Count(*) From A Group By Name Having Count(*) > 1

  如果還查性別也相同大則如下:

  Select Name,***,Count(*) From A Group By Name,*** Having Count(*) > 1

  (三)

  方法一

  declare @max integer,@id integer

  declare cur_rows cursor local for select 主欄位,count(*) from 表名 group by 主欄位 having count(*) >; 1

  open cur_rows

  fetch cur_rows into @id,@max

  while @@fetch_status=0

  begin

  select @max = @max -1

  set rowcount @max

  delete from 表名 where 主欄位 = @id

  fetch cur_rows into @id,@max

  end

  close cur_rows

  set rowcount 0

  方法二

  "重複記錄"有兩個意義上的重複記錄,一是完全重複的記錄,也即所有欄位均重複的記錄,二是部分關鍵欄位重複的記錄,

  比如Name欄位重複,而其他欄位不一定重複或都重複可以忽略。

  1、對於第一種重複,比較容易解決,使用

  select distinct * from tableName就可以得到無重複記錄的結果集。

  如果該表需要刪除重複的記錄(重複記錄保留1條),可以按以下方法刪除

  select distinct * into #Tmp from tableName

  drop table tableName

  select * into tableName from #Tmp

  drop table #Tmp

  發生這種重複的原因是表設計不周產生的,增加唯一索引列即可解決。

  2、這類重複問題通常要求保留重複記錄中的第一條記錄,操作方法如下

  假設有重複的欄位為Name,Address,要求得到這兩個欄位唯一的結果集

  select identity(int,1,1) as autoID, * into #Tmp from tableName

  select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID

  select * from #Tmp where autoID in(select autoID from #tmp2)

  最後一個select即得到了Name,Address不重複的結果集(但多了一個autoID欄位,實際寫時可以寫在select子句中省去此列)

  (四)

  查詢重複

  select * from tablename where id in (

  select id from tablename

  group by id

  having count(id) > 1

  )


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