SQL 查詢重複資料並顯示重複次數
查詢有重複資料的記錄 select * from F group by a,b,c,d having count(*)>1
刪除重複一模一樣的記錄,只保留一條記錄
select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp
例如: id name value 1 a pp 2 a pp 3 b iii 4 b pp 5 b pp 6 c pp 7 c pp 8 c iii id是主鍵 要求得到這樣的結果 id name value 1 a pp 3 b iii 4 b pp 6 c pp 8 c iii
方法1 delete YourTable where [id] not in ( select max([id]) from YourTable group by (name + value)) 方法2 delete a from 表 a left join( select id=min(id) from 表 group by name,value )b on a.id=b.id where b.id is null 查詢及刪除重複記錄的SQL語句 查詢及刪除重複記錄的SQL語句 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,sex,Count(*) From A Group By Name,sex 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 )