如何在 Oracle 的表中查找重复值？

Question

将返回给定列的重复值及其在 Oracle 数据库表中出现次数的最简单的 SQL 语句是什么？

例如：我有一个 JOBS 带列的表 JOB_NUMBER. 。我怎样才能知道我是否有重复的 JOB_NUMBERs，它们被重复了多少次？

Answer 1

SELECT column_name, COUNT(column_name)
FROM table_name
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
)

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

Answer 3

我能想到的最简单的：

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

Answer 4

如果您不需要知道实际的重复项数，则甚至不需要返回列中的计数。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;

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;

Answer 6

如果多列标识唯一行（例如关系表），您可以使用以下内容

使用行IDemp_dept（empid，deptid，startdate，enddate）假设empid和deptid是唯一的，并在这种情况下识别行

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，则使用主键而不是 rowid，例如 id 是 pk 那么

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

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。

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 甲骨文分析 功能 ROW_NUMBER().

假设您想要检查关于基于列构建的唯一索引或主键的重复项（c1, c2, c3）。然后你会走这条路，抚养 ROWID s 行，其中行数由 ROW_NUMBER() 是 >1:

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

下面是执行此操作的 SQL 请求：

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

Answer 11

我知道它是一个旧线程，但这可能会对某些人有所帮助。

如果您需要在检查下面的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;

如果需要的话还可以在 where 子句中添加一些额外的过滤器。

Answer 12

1.解决方案

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

Answer 13

您也可以尝试这样的方法来列出表中的所有重复值，例如 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;