根據條件的列數

Question

我創建了一個oracle查詢，如下所示，查詢工作正常 ，但問題是，我想要一個更多的列，這是名稱的計數，其中類別應該是A和ID應該在1

SELECT name, velocity, COUNT(*) AS count, category FROM section GROUP BY name, velocity 

誰能告訴我，這

Answer 1

SELECT name, velocity, COUNT(*) AS count, 
COUNT(CASE WHEN category = 'A' AND id = 1 THEN 1 END) 
FROM section 
GROUP BY name, velocity 

這應該工作。

如果記錄不符合條件，那麼它將返回一個NULL，並且count跳過NULL字段。

Answer 2

SELECT name, velocity, COUNT(*) AS count, category, 
     (select count(distinct name) from section where category = 'A' and id = 1) 
FROM section 
GROUP BY name, velocity 

Answer 3

事情是這樣的一些解決方案：

SELECT name, velocity, COUNT(*) AS count, 
SUM(CASE WHEN category = 'A' AND id = 1 THEN 1 ELSE 0 END) 
FROM section 
GROUP BY name, velocity