供您参考:
--------------------------------
刪除某字段重復紀錄:
------------------ select distinct boardtype into #Tmp from board
drop table board
select * into board from #Tmp
drop table #Tmp
--------------------------------------------------
在SQL中删除重复记录(多种方法)
-----------------------------(以表employee为例)。
SQL> desc employeeName Null? Type
----------------------------------------- -------- ------------------
emp_id NUMBER(10)
emp_name VARCHAR2(20)
salary NUMBER(10,2)可以通过下面的语句查询重复的记录:SQL> select * from employee;EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
1 sunshine 10000
2 semon 20000
2 semon 20000
3 xyz 30000
2 semon 20000SQL> select distinct * from employee;EMP_ID EMP_NAME SALARY
---------- --------------------------------------- ----------
1 sunshine 10000
2 semon 20000
3 xyz 30000SQL> select * from employee group by emp_id,emp_name,salary having count (*)>1EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
2 semon 20000SQL> select * from employee e1
where rowid in (select max(rowid) from employe e2
where e1.emp_id=e2.emp_id and
e1.emp_name=e2.emp_name and e1.salary=e2.salary);EMP_ID EMP_NAME SALARY
--------- ---------------------------------------- ----------
1 sunshine 10000
3 xyz 30000
2 semon 20000 2. 删除的几种方法:(1)通过建立临时表来实现
SQL> create table temp_emp as (select distinct * from employee)
SQL> truncate table employee; (清空employee表的数据)
SQL> insert into employee select * from temp_emp; (再将临时表里的内容插回来)( 2)通过唯一rowid实现删除重复记录.在Oracle中,每一条记录都有一个rowid,rowid在整个数据库中是唯一的,rowid确定了每条记录是在Oracle中的哪一个数据文件、块、行上。在重复的记录中,可能所有列的内容都相同,但rowid不会相同,所以只要确定出重复记录中那些具有最大或最小rowid的就可以了,其余全部删除。SQL>delete from employee e2 where rowid not in (
select max(e1.rowid) from employee e1 where
e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and e1.salary=e2.salary);--这里用min(rowid)也可以。SQL>delete from employee e2 where rowid <(
select max(e1.rowid) from employee e1 where
e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and
e1.salary=e2.salary);(3)也是通过rowid,但效率更高。SQL>delete from employee where rowid not in (
select max(t1.rowid) from employee t1 group by
t1.emp_id,t1.emp_name,t1.salary);--这里用min(rowid)也可以。EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
3 xyz 30000
2 semon 20000
--------------------------------
刪除某字段重復紀錄:
------------------ select distinct boardtype into #Tmp from board
drop table board
select * into board from #Tmp
drop table #Tmp
--------------------------------------------------
在SQL中删除重复记录(多种方法)
-----------------------------(以表employee为例)。
SQL> desc employeeName Null? Type
----------------------------------------- -------- ------------------
emp_id NUMBER(10)
emp_name VARCHAR2(20)
salary NUMBER(10,2)可以通过下面的语句查询重复的记录:SQL> select * from employee;EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
1 sunshine 10000
2 semon 20000
2 semon 20000
3 xyz 30000
2 semon 20000SQL> select distinct * from employee;EMP_ID EMP_NAME SALARY
---------- --------------------------------------- ----------
1 sunshine 10000
2 semon 20000
3 xyz 30000SQL> select * from employee group by emp_id,emp_name,salary having count (*)>1EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
2 semon 20000SQL> select * from employee e1
where rowid in (select max(rowid) from employe e2
where e1.emp_id=e2.emp_id and
e1.emp_name=e2.emp_name and e1.salary=e2.salary);EMP_ID EMP_NAME SALARY
--------- ---------------------------------------- ----------
1 sunshine 10000
3 xyz 30000
2 semon 20000 2. 删除的几种方法:(1)通过建立临时表来实现
SQL> create table temp_emp as (select distinct * from employee)
SQL> truncate table employee; (清空employee表的数据)
SQL> insert into employee select * from temp_emp; (再将临时表里的内容插回来)( 2)通过唯一rowid实现删除重复记录.在Oracle中,每一条记录都有一个rowid,rowid在整个数据库中是唯一的,rowid确定了每条记录是在Oracle中的哪一个数据文件、块、行上。在重复的记录中,可能所有列的内容都相同,但rowid不会相同,所以只要确定出重复记录中那些具有最大或最小rowid的就可以了,其余全部删除。SQL>delete from employee e2 where rowid not in (
select max(e1.rowid) from employee e1 where
e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and e1.salary=e2.salary);--这里用min(rowid)也可以。SQL>delete from employee e2 where rowid <(
select max(e1.rowid) from employee e1 where
e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and
e1.salary=e2.salary);(3)也是通过rowid,但效率更高。SQL>delete from employee where rowid not in (
select max(t1.rowid) from employee t1 group by
t1.emp_id,t1.emp_name,t1.salary);--这里用min(rowid)也可以。EMP_ID EMP_NAME SALARY
---------- ---------------------------------------- ----------
1 sunshine 10000
3 xyz 30000
2 semon 20000
print '改列有重复值'
else
print '改列没有重复值'
==============>
SELECT distinct A.* FROM TB A,TB B WHERE A.COL=B.COL AND A.ID<>B.ID--假设ID是表主键
if (select count(colName) from tablename)<>(select count(distinct colName) from tablename)
print '改列有重复值'
else
print '改列没有重复值'