mysql - 计算Mysql表中的重复记录？

Question

我有桌子，结构如下。

表

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

与 AAA 和 BBB 重复的名称。我想要的最终结果是对这些重复记录的计数。

结果应该是这样的： 重复产品总数（2）

Answer 1

方法是有一个嵌套查询，每个重复一行，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

对于列表：

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

对于总计数：

    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 4

为什么不把它包装在一个子查询中：

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

请参阅带有演示的 SQL Fiddle

Answer 5

接受的答案计算有重复的行数，而不是重复的数量。如果要计算重复的实际数量，请使用：

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

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

) x

这样做是将分组中的重复项加起来，然后减去具有重复项的记录数量。原因是按总计分组并非所有重复项，每个分组的一条记录是唯一行。

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)

Answer 7

我在 PHP 中对我自己的表使用此查询，但它只给我一个结果，而我想要每个用户名的重复数量，这可能吗？

SELECT count(*) AS duplicate_count
FROM (
 SELECT username FROM login_history
 GROUP BY username HAVING COUNT(time) > 1
) AS t;