SELECT COUNT MAX（值），其中

Question

你好，你在圖片中看到連接，我想用這個查詢

SELECT count(idmilestone) 
FROM milestoneevent 
WHERE max(idmilestone=1) 

我想在我的情況來計算所有與最後一個里程碑= 1文件提取數據表它必須回到5，因爲兩個文件了具有里程碑意義現在2請幫我實現這個

Answer 1

select count('id') 
from (select idfile, max(idmilestone) as max_idmilestone 
     from milestoneevent 
     group by idfile 
    ) d 
where max_idmilestone = 1; 

Answer 2

嘗試這個

SELECT count(idmilestone) 
FROM milestoneevent 
WHERE idfile NOT IN(SELECT idfile 
    FROM milestoneevent 
    WHERE idfile > 1) 

Answer 3

對於您提供的數據，里程碑數量在不斷增加。如果這是大致如此，你可以簡單地做：

select count(*) 
from (select idfile, max(idmilestone) as max_idmilestone 
     from milestoneevent 
     group by idfile 
    ) m 
where max_idmilestone = 1; 

或者，您可以使用dat定義的最後一個：

select count(*) 
from milestonemevent me 
where me.dat = (select max(me2.dat) 
       from milestonemevent me2 
       where me.idfile = me2.idfile 
       ) and 
     me.idmilestone = 1; 

Answer 4

請試試這個，它會給idmilestone的計數其是至少一個，即1

SELECT count(idmilestone) FROM milestoneevent 
WHERE idmilestone =(SELECT MIN(idmilestone) FROM milestoneevent) 

，如果你想指望它等於1，那麼試試這個

SELECT count(idmilestone) FROM milestoneevent 
WHERE idmilestone =1 

Answer 5

您可以使用此一LEFT JOIN：

SELECT t1.id, t1.idfile, t1.idmilestone 
FROM milestoneevent AS t1 
LEFT JOIN milestoneevent AS t2 
    ON t1.idfile = t2.idfile AND t1.dat < t2.dat 
WHERE t1.idmilestone = 1 AND t2.id IS NULL 

Demo here

要計算使用COUNT：

SELECT COUNT(*) 
FROM milestoneevent AS t1 
LEFT JOIN milestoneevent AS t2 
    ON t1.idfile = t2.idfile AND t1.dat < t2.dat 
WHERE t1.idmilestone = 1 AND t2.id IS NULL 
GROUP BY t1.idfile 

Answer 6

試試這個：

SELECT COUNT(*) 
FROM (
    SELECT idmilestone 
    FROM milestoneevent 
    GROUP BY idmilestone 
    HAVING COUNT(*) = 1 
) 
WHERE idmilestone=1