如何:

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;

按COUNT聚合列，然后使用HAVING子句查找出现多次的值。

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

我能想到的最简单的:

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

如何:

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;

我通常使用Oracle分析函数ROW_NUMBER()。

假设您想检查构建在列(c1, c2, c3)上的唯一索引或主键的副本。 然后你将这样做，打开ROW_NUMBER()带来的行数为>1的行数的ROWID s:

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)

另一种方法:

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)。它是删除或更新重复行的更好方法。