Question

假设我有一个名为test的下表，其中包含2列A和B
A B
------
1 2
2 3
1 2
3 4
我想使用一个查询，该查询只返回基于A和B列组合的重复行数（在本例中为1和3），因此返回的计数应为{{1} }。
2（查询在这里），谢谢。

Answer 1

SELECT A, B, COUNT(*) as Count FROM Test GROUP BY A, B HAVING COUNT(*) > 1

Answer 2

如果我理解正确，如果你的例子中有另一行（2,3）那么计数应该是4.如果是这样，请使用：

SELECT 'Duplicates' as warning,sum(cnt) FROM (
    SELECT a,b,COUNT(*) as cnt
    FROM YourTable
    GROUP BY a,b
    HAVING count(*) > 1
)

Answer 3

要成对使用，

SELECT CONCAT(A,'-',B) AS Duplicate Pair,COUNT(A) AS COUNT FROM `test` GROUP BY A,B HAVING COUNT(A) > 1;

OR 为了个人使用，

SELECT A AS Duplicate1,B AS Duplicate2,COUNT(A) AS COUNT FROM `test` GROUP BY A,B HAVING COUNT(A) > 1;

Answer 4

您可以使用子查询：

select 'Duplicates' as warning, count(*) as rowcount
from (select a, b, count(*) as cnt
      from test t
      group by a, b
      having cnt > 1
     ) t;

仅基于2列计算重复行

4 个答案: