MySQL的計數獨特的行值

Question

TABLE quotation

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

我如何可以查詢有多少不同的客戶TABLE quotation存在嗎？我不希望重複的條目被計入多次。

我需要的答案是2，在1行，因爲唯一的非重複條目是（25,26）。

Answer 1

select count(distinct clientid) from quotation 

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Answer 2

我發現我嘗試了MySQL的5.x的數據庫上執行下面出路

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

Answer 3

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

Answer 4

。

id是一個整數，clientid是一個整數。我填充了兩行：在本例中如果你想2個或多個元素

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

，更換= 2以上>= 2：

id clientid 
1 25 
2 25 

這個SQL查詢將打印具有完全相同2個元素的行。

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

Answer 5

如果要計算唯一條目的總數，這將返回列計數中的數字。

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

如果要計算具有重複行的條目總數，請使用以下mysql。

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