删除反复行SQL实验简单举例
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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表中插入反复行
SQL> commit;
SQL> select count(*) from emp;
COUNT(*)
----------
28
以下举例单字段删除反复行
例1：查询出反复记录（单字段）
SQL> select * from empwhere empno in (select empno from emp group by empno having count
(empno) > 1);
--查找出emp表中多余的反复记录，反复记录是依据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：删除表中多余的反复记录，仅仅留有rowid最小的记录
SQL> delete from empwhere 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);
--删除表中多余的反复记录。反复记录是依据单个字段empno来判读
--保留rowid最小的行记录信息
14 rows deleted.
SQL> select * from emp ; --反复的行已经删除
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：查询表中反复的记录（多字段）
SQL> select * from emp awhere (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：删除表中反复记录（多个字段），仅仅保留rowid最小的记录
SQL> delete from emp awhere (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：查询表中多余的反复记录（多字段）。不包括rowid最小的记录
SQL> select * from emp awhere (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.
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