计算Mysql表中的重复记录？

Question

我有桌子，下面的结构。

tbl

id   name  
1    AAA
2    BBB
3    BBB
4    BBB
5    AAA
6    CCC

select count(name) c from tbl
group by name having c >1

返回此结果的查询：

AAA(2)  duplicate
BBB(3)  duplicate
CCC(1)  not duplicate

重复的名称为AAA和BBB。最终结果，我想要的是这些重复记录的数量。

结果应该是这样的：      重复产品总数（ 2 ）

Answer 1

方法是使嵌套查询每个副本有一行，外部查询只返回内部查询结果的计数。

SELECT count(*) AS duplicate_count
FROM (
 SELECT name FROM tbl
 GROUP BY name HAVING COUNT(name) > 1
) AS t

Answer 2

使用IF语句获得所需的输出：

SELECT name, COUNT(*) AS times, IF (COUNT(*)>1,"duplicated", "not duplicated") AS duplicated FROM <MY_TABLE> GROUP BY name

输出：

AAA 2 duplicated
BBB 3 duplicated
CCC 1 not duplicated

Answer 3

为什么不将它包装在子查询中：

SELECT Count(*) TotalDups
FROM
(
    select Name, Count(*)
    from yourTable
    group by name
    having Count(*) > 1
) x

请参阅SQL Fiddle with Demo

Answer 4

列表：

SELECT COUNT(`name`) AS adet, name
FROM  `tbl` WHERE `status`=1 GROUP BY `name`
ORDER BY `adet`  DESC

总计数：

    SELECT COUNT(*) AS Total
    FROM (SELECT COUNT(name) AS cou FROM tbl GROUP BY name HAVING cou>1 ) AS virtual_tbl 

//总计：5

Answer 5

接受的答案计算具有重复项的行数，而不是重复数量。如果您要计算实际重复次数，请使用以下命令：

SELECT COALESCE(SUM(rows) - count(1), 0) as dupes FROM(

    SELECT COUNT(1) as rows
    FROM `yourtable`
    GROUP BY `name`
    HAVING rows > 1

) x

这样做会使组中的重复项总数增加，但随后减去具有重复项的记录数量。原因是group by total不是全部重复，每个分组的一个记录是唯一的行。

小提琴：http://sqlfiddle.com/#!2/29639a/3

Answer 6

SQL代码是：

SELECT VERSION_ID, PROJECT_ID, VERSION_NO, COUNT(VERSION_NO) AS dup_cnt
FROM MOVEMENTS
GROUP BY VERSION_NO
HAVING (dup_cnt > 1 && PROJECT_ID = 11660)