删除重复行SQL举例

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删除重复行SQL实验简单举例

说明：实验按顺序进行，前后存在关联性，阅读时请注意，打开目录更便于查看。

构造实验环境：

SQL> select count(*) from emp;
COUNT(*)
----------
14
SQL> alter table EMP drop constraint PK_EMP CASCADE;
--删除主键约束
SQL> insert into EMP select * from EMP;
--向EMP表中插入重复行
SQL> commit;
SQL> select count(*) from emp;
COUNT(*)
----------
28

下面举例单字段删除重复行

例1：查询出重复记录（单字段）

SQL> select * from emp
where empno in (select empno from emp group by empno having count
(empno) > 1);
--查找出emp表中多余的重复记录，重复记录是根据empno来判读

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7839 KING PRESIDENT 17-NOV-81 5000 10
7839 KING PRESIDENT 17-NOV-81 5000 10
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7900 JAMES CLERK 7698 03-DEC-81 950 30

28 rows selected.

例2：删除表中多余的重复记录，只留有rowid最小的记录

SQL> delete from emp
where empno in (select empno from emp group by empno having count
(empno) > 1)
and rowid not in (select min(rowid) from emp group by empno having count(empno
)>1);
--删除表中多余的重复记录，重复记录是根据单个字段empno来判读
--保留rowid最小的行记录信息
14 rows deleted.

SQL> select * from emp ; --重复的行已经删除

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7839 KING PRESIDENT 17-NOV-81 5000 10

14 rows selected.

SQL> insert into emp select * from emp;

SQL> insert into emp values(8888,‘HYL‘,‘DBA‘,7839,sysdate,2000,‘‘,60);

1 row created.

SQL> commit;

Commit complete.

SQL> select * from emp;

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7839 KING PRESIDENT 17-NOV-81 5000 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7839 KING PRESIDENT 17-NOV-81 5000 10
8888 HYL DBA 7839 06-JUL-14 2000 60

29 rows selected.

多字段下：

例3：查询表中重复的记录（多字段）

SQL> select * from emp a
where (a.empno,a.deptno) in (select empno,deptno from emp group by empno,deptno having
count(*) > 1);

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7900 JAMES CLERK 7698 03-DEC-81 950 30
7900 JAMES CLERK 7698 03-DEC-81 950 30
7839 KING PRESIDENT 17-NOV-81 5000 10
7839 KING PRESIDENT 17-NOV-81 5000 10
7566 JONES MANAGER 7839 02-APR-81 2975 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30

28 rows selected.

例4：删除表中重复记录（多个字段），只保留rowid最小的记录

SQL> delete from emp a
where (a.empno,a.deptno) in (select empno,deptno from emp group by empno,deptno having
count(*) > 1)
and rowid not in (select min(rowid) from emp group by empno,deptno having count(*)>1);

14 rows deleted.

SQL> select * from emp;

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7839 KING PRESIDENT 17-NOV-81 5000 10
8888 HYL DBA 7839 06-JUL-14 2000 60

15 rows selected.

SQL> rollback
2 ;

Rollback complete.

SQL> select * from emp;

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7839 KING PRESIDENT 17-NOV-81 5000 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7839 KING PRESIDENT 17-NOV-81 5000 10
8888 HYL DBA 7839 06-JUL-14 2000 60

29 rows selected.

例5：查询表中多余的重复记录（多字段），不包含rowid最小的记录

SQL> select * from emp a
where (a.empno,a.deptno) in (select empno,deptno from emp group by empno,deptno having
count(*) > 1)
and rowid not in (select min(rowid) from emp group by empno,deptno having count(*)>1);

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7900 JAMES CLERK 7698 03-DEC-81 950 30
7839 KING PRESIDENT 17-NOV-81 5000 10
7566 JONES MANAGER 7839 02-APR-81 2975 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30

14 rows selected.

SQL> commit;

Commit complete.

SQL> select * from emp; --emp表实际数据

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7839 KING PRESIDENT 17-NOV-81 5000 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7566 JONES MANAGER 7839 02-APR-81 2975 20
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7839 KING PRESIDENT 17-NOV-81 5000 10
8888 HYL DBA 7839 06-JUL-14 2000 60

29 rows selected.

***********************************************声明************************************************

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删除重复行SQL举例

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原文地址：http://blog.csdn.net/huangyanlong/article/details/37355671

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