我有一個具有以下字段自聯接提取事件表中的相關記錄?
Time | Status
2016-01-21 16:11:00 | Connected
2016-01-21 16:51:00 | Disconnected
2016-01-21 17:01:00 | Connected
2016-01-21 17:10:00 | Status X
2016-01-21 17:20:00 | Status Y
2016-01-21 17:25:00 | Disconnected
2016-01-21 17:30:00 | Connected
2016-01-21 17:32:00 | Disconnected
我想要的輸出是這樣
Disconnected Connected
2016-01-21 16:51:00 | 2016-01-21 17:01:00
2016-01-21 17:25:00 | 2016-01-21 17:30:00
2016-01-21 17:32:00 |
等的表。也就是說,我想,以顯示與服務器斷開連接時的數據。
我寫這樣
select B.Time, A.Time
from (select Time
from table
where Status = 'Connected') as A, table B
where B.Status = 'Disconnected'
and B.Time < A.Time;
我輸出查詢
Disconnected Connected
2016-01-21 16:51:00 2016-01-21 17:01:00
2016-01-21 16:51:00 2016-01-21 17:30:00
也就是說,我讓所有的相關事件比它更大的每個斷開連接的事件。不過,我想只不是每一行斷開事件時,第一連接的事件。我能做什麼?