导读:1建站知识案例：一个应用表中的一个字段是主键，向表中插入数据时，先把数据放在临时表中（没有主键）然后再插入应用表企业网站建设网站建设哪家好。

这时候如果临时表中有重复数据，无论是主键字段businessid有重复，还是一整行有重复都会报出违反唯一主键约束错误。

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

1、查询表中的重复数据a.重复一个字段

b.重复多个字段

c.重复一整行

创建测试表：

复制代码 代码如下:

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');

---------------以下为重复数据----------------------------------------------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');

对于a的情况,只有businessid重复

复制代码 代码如下:

select * from cfa where businessid in (select businessid from 网站建设教程cfa group by businessid having count(businessid)>1);

如果是b的情况，businessid网站建设公司 和name同时存在重复

复制代码 代码如下:

select * from cfa where (businessid,customer) in (select businessid,customer from cfa group by businessid,customer having count(*)>1);

对于c的情况，重复一整行

参考b的方法：

复制代码 代码如下:

select * from cfa where (businessid,customer,branchcode,data_date) in (select * from cfa group by businessid,customer,branchcode,data_date having count(*)>1);

2、删除表中的重复数据a情况，删除表中多余的重复记录，重复记录是根据单个字段（businessid）来判断，只留有rowid最小的记录

也可以只保留rowid不是最小记录，需要把代码中的min改为max这里不再赘述。

复制代码 代码如下:

delete from cfawhere businessid in (select businessidfrom cfagroup by businessidhaving count(businessid) > 1)and rowid not in (select min(rowid)from cfagroup by businessidhaving count(businessid) > 1);

或者，使用下面更简单高效的语句

复制代码 代码如下:

DELETE FROM cfa tWHERE t.ROWID >(SELECT MIN(X.ROWID) FROM cfa X WHERE X.businessid = t.businessid);

b情况，删除表中多余的重复记录（多个字段），只留有rowid最小的记录

复制代码 代码如下:

delete from cfawhere (businessid,customer) in (select businessid,customerfrom cfagroup by businessid,customerhaving count(*) > 1)and rowid not in (select min(rowid)from cfagroup by businessid,customerhaving count(*) > 1);

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