SQL中的简单数据透视表转置

Question

我正在努力理解如何使用pivot操作符来转置表但我无法弄明白。任何帮助都会很棒。这是我需要转置的查询。

SELECT 
    sum(delayCarrier>0)  AS 'Carrier Delay',
    sum(delayWeather>0) AS 'Weather Delay',
    sum(delayTraffic>0) AS 'Air Traffic Delay',
    sum(delaySecurity>0)  AS 'Security Delay'
FROM flights

这是表格版本。

我需要它阅读：

'TypeOfDelay','Frequency'
-------------------------
Carrier Delay | 32093
Weather Delay | 4887
Air Traffic Delay | 40730
Security Delay | 215

抱歉，我知道这个问题已经被问了很多，我看了很多，但我似乎无法获得任何直觉。提前谢谢。

Answer 1

这是一个查询，它可以为您提供所需的输出，但我不能说老实说这是一个支点，或者它很漂亮。

SELECT 'Carrier Delay' AS TypeOfDelay, SUM(delayCarrier > 0) AS Frequency
FROM flights
UNION ALL
SELECT 'Weather Delay' AS TypeOfDelay, SUM(delayWeather > 0) AS Frequency
FROM flights
UNION ALL
SELECT 'Air Traffic Delay' AS TypeOfDelay, SUM(delayTraffic > 0) AS Frequency
FROM flights
UNION ALL
SELECT 'Security Delay' AS TypeOfDelay, SUM(delaySecurity > 0) AS Frequency
FROM flights