mysql计数唯一的行值

Question

TABLE quotation

id  clientid
1   25
2   25
3   25
4   25
5   26

如何查询TABLE quotation中存在多少个不同的客户？我不希望重复的条目被多次计算。

我需要答案为2，排成一行，因为唯一不重复的条目是（25，26）。

Answer 1

select count(distinct clientid) from quotation

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Answer 2

我找到了出路

SELECT COUNT(*) as total FROM (SELECT COUNT(*) FROM quotation GROUP BY
clientid) t1

Answer 3

我在MySQL 5.x数据库上尝试了以下内容。

id是一个整数，clientid是一个整数。我填充了两行：

id  clientid
1   25
2   25

此SQL查询将打印具有两个元素的行：

select * from test1 group by clientid having count(*) = 2;

如果您需要2个或更多元素，请将上面示例中的= 2替换为>= 2。

select * from test1 group by clientid having count(*) >= 2;

Answer 4

如果要计算唯一条目的总数，这将返回列数中的数字。

SELECT COUNT(*) as total FROM (SELECT COUNT(*) FROM quotation GROUP BY clientid having count(*) > 1) t1

如果要计算具有重复行的条目总数，请使用以下mysql。

SELECT COUNT(*) as total FROM (SELECT COUNT(*) FROM quotation GROUP BY clientid having count(*) >= 2) t1

Answer 5

SELECT clientid, COUNT(clientid) FROM quotation 
GROUP BY clientid