如何在 Oracle 的表中查找重复值？

按 COUNT 聚合列，然后使用 HAVING 子句查找出现大于一次的值。

SELECT column_name, COUNT(column_name)
FROM table_name
GROUP BY column_name
HAVING COUNT(column_name) > 1;

另一种方式：

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。

我能想到的最简单的：

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

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包含计数。例如

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

怎么样：

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

要回答上面的例子，它看起来像：

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

如果多个列标识唯一行（例如关系表），您可以使用以下

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 然后

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);

正在做

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

将为您提供重复行的 ID。

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

我通常使用 Oracle Analytic 函数 ROW_NUMBER()。

假设您要检查有关基于列（c1、c2、c3）构建的唯一索引或主键的重复项。然后你会这样走，调出 ROWID 行，其中 ROW_NUMBER() 带来的行数是 >1：

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

我知道它是一个旧线程，但这可能会对某些人有所帮助。

如果您需要在下面检查重复使用时打印表格的其他列：

select * from table where column_name in
(select ing.column_name from table ing group by ing.column_name having count(*) > 1)
order by column_name desc;

如果需要，还可以在 where 子句中添加一些额外的过滤器。

这是执行此操作的 SQL 请求：

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

1.解决方案

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

你也可以尝试这样的事情来列出表中的所有重复值说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;