SQL：計數第

Question

SELECT Impressions.Campaign_id as C_id, Verticals.Vertical_Name as V_name 
FROM Impressions 
Inner Join Verticals ON Impressions.Campaign_id = Verticals.Campaign_id; 

上述查詢產生的結果是：

C_id   V_name 
    ID1   Travel 
    ID2   Retail 
    ID3    Demo 
    ID4    Demo 
    ID5   Travel 
    ID6    Demo 

我希望它返回VERTICAL_NAME列出現的次數的計數。在這種情況下，結果應該如下所示：

V_id Count 
Demo  3 
Travel 2 
Retail 1 

我該如何解決這個問題？

Answer 1

你需要COUNT，不MAX和GROUP BY然後垂直名：

SELECT Verticals.Vertical_Name as V_name, COUNT(*) AS [Count] 
FROM Impressions 
Inner Join Verticals ON Impressions.Campaign_id = Verticals.Campaign_id 
GROUP BY Verticals.Vertical_Name