1、查找表中多余的重復記錄，重復記錄是根據單個字段（peopleId）來判斷 ``` select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1) ``` 2、刪除表中多余的重復記錄，重復記錄是根據單個字段（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、查找表中多余的重復記錄（多個字段） ``` select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) ``` 4、刪除表中多余的重復記錄（多個字段），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,seqhaving count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq havingcount(*)>1) ``` 5、查找表中多余的重復記錄（多個字段），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,seqhaving count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq havingcount(*)>1) ``` (二) 比方說，在A表中存在一個字段“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”值存在重復的項. ``` 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 主字段,count(*) from 表名 group by 主字段 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 主字段 = @id fetch cur_rows into @id,@max end close cur_rows set rowcount 0 ``` 方法二 　有兩個意義上的重復記錄，一是完全重復的記錄，也即所有字段均重復的記錄，二是部分關鍵字段重復的記錄，比如Name字段重復，而其他字段不一定重復或都重復可以忽略。 1、對于第一種重復，比較容易解決，使用以下語句就可以得到無重復記錄的結果集。 ``` select distinct * from tableName ``` 如果該表需要刪除重復的記錄（重復記錄保留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 ``` 發生這種重復的原因是表設計不周產生的，增加唯一索引列即可解決。 2、這類重復問題通常要求保留重復記錄中的第一條記錄，操作方法如下 假設有重復的字段為Name,Address，要求得到這兩個字段唯一的結果集 ``` select identity(int,1,1) as autoID, * into #Tmp from ``` 假設有重復的字段為Name,Address，要求得到這兩個字段唯一的結果集 ``` 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) ``` 最后一個select即得到了Name，Address不重復的結果集（但多了一個autoID字段，實際寫時可以寫在select子句中省去此列） (四)查詢重復 ``` select * from tablename where id in ( select id from tablename group by id having count(id) > 1 ) ```