如何在Oracle的表中find重复值？

什么是最简单的SQL语句，将返回给定列的重复值以及Oracle数据库表中出现的次数？

例如：我有JOB_NUMBER列的JOBS表。 我如何知道我是否有任何重复的JOB_NUMBER ，以及它们重复了多less次？

Answer 1

 select column_name, count(column_name) from table group by column_name having count (column_name) > 1; 

Answer 2

其他方式：

 SELECT * FROM TABLE A WHERE EXISTS ( SELECT 1 FROM TABLE WHERE COLUMN_NAME = A.COLUMN_NAME AND ROWID < A.ROWID ) 

当column_name上有索引时，工作正常（足够快）。 这是删除或更新重复行的更好方法。

Answer 3

最简单的我可以想到：

 select job_number, count(*) from jobs group by job_number having count(*) > 1; 

Answer 4

如果您不需要知道重复的实际数量，您甚至不需要在返回的列中进行计数。 例如

 SELECT column_name FROM table GROUP BY column_name HAVING COUNT(*) > 1 

Answer 5

怎么样：

 SELECT <column>, count(*) FROM <table> GROUP BY <column> HAVING COUNT(*) > 1; 

回答上面的例子，它看起来像：

 SELECT job_number, count(*) FROM jobs GROUP BY job_number HAVING COUNT(*) > 1; 

Answer 6

在多列标识唯一行（例如关系表）的情况下，可以使用以下内容

使用行ID例如emp_dept（empid，deptid，startdate，enddate）假设empid和deptid是唯一的，并在这种情况下标识行

 select oed.empid, count(oed.empid) from emp_dept oed where exists ( select * from emp_dept ied where oed.rowid <> ied.rowid and ied.empid = oed.empid and ied.deptid = oed.deptid ) group by oed.empid having count(oed.empid) > 1 order by count(oed.empid); 

如果这样的表有主键，那么使用主键而不是rowid，例如id是pk

 select oed.empid, count(oed.empid) from emp_dept oed where exists ( select * from emp_dept ied where oed.id <> ied.id and ied.empid = oed.empid and ied.deptid = oed.deptid ) group by oed.empid having count(oed.empid) > 1 order by count(oed.empid); 

Answer 7

干

 select count(j1.job_number), j1.job_number, j1.id, j2.id from jobs j1 join jobs j2 on (j1.job_numer = j2.job_number) where j1.id != j2.id group by j1.job_number 

会给你重复的行ID。

Answer 8

 SELECT SocialSecurity_Number, Count(*) no_of_rows FROM SocialSecurity GROUP BY SocialSecurity_Number HAVING Count(*) > 1 Order by Count(*) desc 

Answer 9

我通常使用Oracle分析函数ROW_NUMBER（） 。

假设您想检查您拥有的关于build立在列（ c1 ， c2 ， c3 ）上的唯一索引或主键的重复项。 那么你ROWID ，提出了ROW_NUMBER()带来的行数>1的行的ROWID 。

 Select * From Table_With_Duplicates Where Rowid In (Select Rowid From (Select Rowid, ROW_NUMBER() Over ( Partition By c1 || c2 || c3 Order By c1 || c2 || c3 ) nbLines From Table_With_Duplicates) t2 Where nbLines > 1) 

Answer 10

解决scheme

 select * from emp where rowid not in (select max(rowid) from emp group by empno); 

Answer 11

另外你可以尝试这样的事情列出所有重复的值在表中说reqitem

 SELECT count(poid) FROM poitem WHERE poid = 50 AND rownum < any (SELECT count(*) FROM poitem WHERE poid = 50) GROUP BY poid MINUS SELECT count(poid) FROM poitem WHERE poid in (50) GROUP BY poid HAVING count(poid) > 1;