SQL query、计数和组通过

Question

如果我有这样的数据:

+---+----+
|Key|Name|
+---+----+
|1  |Dan |
+---+----+
|2  |Tom |
+---+----+
|3  |Jon |
+---+----+
|4  |Tom |
+---+----+
|5  |Sam |
+---+----+
|6  |Dan |
+---+----+

什么是SQL query带回来的记录 Name 重复2个或更多次？

因此结果，我希望是

 +---+
 |Tom|
 +---+
 |Dan|
 +---+

Answer 1

不能简单...

Select
Name,
Count(Name) As Count
From
Table
Group By
Name
Having
Count(Name) > 1
Order By
Count(Name) Desc

这也可以扩展，以删除重复:

Delete
From
Table
Where
Key In (
    Select
    Max(Key)
    From
    Table
    Group By
    Name
    Having
Count(Name) > 1)

Answer 2

select name from table group by name having count(name) > 1

Answer 3

这也可以通过加入该表本身，

SELECT DISTINCT t1.name
FROM    tbl t1
        INNER JOIN tbl t2
        ON      t1.name = t2.name
WHERE   t1.key         != t2.key;