給多個where子句的生啤酒

Question

我做這樣的事情

SELECT 
    start.time AS startTime, 
    finish.time AS finishTime 
FROM Train 
WHERE _id = 3 AS start, 
WHERE _id = 5 AS finish; 

的事情是有在SQL任何等同於這一點，或者我要創建兩個不同的SELECT語句。

Answer 1

假設_id是你的主鍵，你可以做一個嵌套SELECT：

SELECT 
    (SELECT start.time FROM Train Where _id=3) AS start 
, (SELECT finish.time FROM Train Where _id=5) AS finish 

Answer 2

另一種使用條件彙總：

select min(case when _id = 3 then time end) as start_time, 
     max(case when _id = 5 then time end) as end_time 
from t 
where _id in (3, 5); 

Answer 3

SELECT 
LAG(time, 2, 0) OVER() AS startTime 
time AS finishTime, 
FROM Train 
WHERE _id = 5 
ORDER BY _id; 

如果你能calulate開始和結束時間之間的偏移量，可以使用LAG函數訪問前一行的值。如果你不能，請提供完整的查詢，或使用@Gordon Linoff解決方案。