Question

同一个表中,如何写SQL语句查找某一字段重复的记录?

如下表,，A、B、C三个字段，
A B C
10 S P
20 T P
30 R Q
40 W L
50 Y Q
我想找出的结果是：10、20、30和50

Answer 1

个人认为单纯的使用SQL语句来实现是非常困难的。可以使用据体的某种语言（c,c#,java,.net）等来辅助实现此种功能。

Answer 2

查询C字段有重复的记录吗?
如果是小表可以这样写:
select a from tabname
where c in
(select c from tabname group by c having count(1) >1 )
大表(需建c列索引):
select a from tabname a
where exists (select c from tabname b where b.c=a.c group by c having count(1) >1 )

Answer 3

SELECT * FROM tab WHERE C in (
SELECT C
FROM tab
GROUP BY C
HAVING COUNT(A) > 1 )

Answer 4

select A from 表
group by A
having count(C)>=2

Answer 5

select A FROM 表
where C in (
SELECT C FROM 表
group by C
having count(C)>1)