[英]Get Values From SQL Table
我有看起來像這樣的表:
FlightLeg
+------+-----+-------+------+---------------------+---------------------+-------+
| FLNO | Seq | FromA | ToA | DeptTime | ArrTime | Plane |
+------+-----+-------+------+---------------------+---------------------+-------+
| 1000 | 1 | DFW | LOG | 2020-01-01 01:10:20 | 2020-01-01 01:13:40 | 7 |
| 1010 | 1 | LAX | ORD | 2020-01-01 01:13:10 | 2020-01-01 01:16:20 | 3 |
| 1020 | 1 | LOG | JFK | 2020-01-01 01:05:40 | 2020-01-01 01:06:20 | 9 |
| 1030 | 1 | LAX | INT | 2020-01-01 01:11:20 | 2020-01-01 01:16:10 | 6 |
| 1040 | 1 | LAX | LGA | 2020-02-01 01:15:30 | 2020-01-01 01:21:00 | 1 |
| 1010 | 2 | ORD | JFK | 2020-01-01 01:17:10 | 2020-01-01 01:20:20 | 3 |
| 1020 | 2 | JFK | DFW | 2020-01-01 01:07:20 | 2020-01-01 01:10:20 | 9 |
| 1030 | 2 | INT | DFW | 2020-01-01 01:17:20 | 2020-01-01 01:18:00 | 6 |
| 1020 | 3 | DFW | INT | 2020-01-01 01:11:10 | 2020-01-01 01:11:40 | 7 |
| 1020 | 4 | INT | LAX | 2020-01-01 01:12:20 | 2020-01-01 01:15:10 | 7 |
+------+-----+-------+------+---------------------+---------------------+-------+
和這個:
飛行
+------+--------+---------+
| FLNO | Meal | Smoking |
+------+--------+---------+
| 1000 | Bistro | Y |
| 1010 | Meal | N |
| 1020 | Meal | Y |
| 1030 | Snack | N |
| 1040 | Meal | N |
+------+--------+---------+
我正在嘗試編寫一個查詢,在該查詢中,對於具有兩條以上航程的每個航班,檢索航班號(FLNO),首個出發城市(FromA)和最終到達的城市。 飛行序列可以以任意整數開始,並且可以由任意整數偏移量分隔。
這是我到目前為止的內容:
SELECT FlightLeg.FLNO, (
SELECT FlightLeg.FromA
FROM FlightLeg
INNER JOIN Flight
ON FlightLeg.FLNO=Flight.FLNO
GROUP BY FlightLeg.FLNO
HAVING COUNT(*) > 2),
(
SELECT FlightLeg.ToA
FROM FlightLeg
INNER JOIN Flight
ON FlightLeg.FLNO=Flight.FLNO
GROUP BY FlightLeg.FLNO
HAVING COUNT(*) > 2)
FROM FlightLeg
INNER JOIN Flight
ON FlightLeg.FLNO=Flight.FLNO
GROUP BY FlightLeg.FLNO
HAVING COUNT(*) > 2;
我只能輸出正確飛行的第一個序列的FLNO,FromA和ToA。
預期產量:
+------+-------+------+
| FLNO | FromA | ToA |
+------+-------+------+
| 1020 | LOG | LAX |
+------+-------+------+
我想我真的很接近,但是我不確定如何為最小的序列找到FromA,為最大的序列找到ToA。
有人可以幫忙嗎? 謝謝!
解決此問題的一種方法是使用自聯接和派生表,如下所示:
select flight_start.flno, flight_start.froma, flight_end.toa
from flightleg flight_start
join flightleg flight_end on flight_start.flno = flight_end.flno
join (
select
flno,
min(seq) origin,
max(seq) destination
from flightleg
group by flno
having count(*) > 2
) min_max_seq
on flight_start.flno = min_max_seq.flno
and flight_start.seq = min_max_seq.origin
and flight_end.seq = min_max_seq.destination
用作派生表的查詢確定每個航班的最低和最高序號,並且第一個聯接使用較低的序號檢索始發機場,而第二個聯接使用較高的序號檢索目的機場。 支路的數量在派生表的having
子句中確定。
附帶一提:如果序列號不是訂單的良好決定因素,則可以使用日期來確定訂單或支路。
select x.flno,
Max( if( y.DeptTime = x.starter, y.FromA, null )) FirstLegFrom,
Max( if( y.DeptTime = x.starter, y.DeptTime, null )) FirstLegStart,
Max( if( y.DeptTime = x.ender, y.ToA, null )) LastLegFrom,
Max( if( y.DeptTime = x.ender, y.ArrTime, null )) LastLegArrival
from(
select flno, min(depttime) as starter, max(depttime) as ender
from flightleg
group by flno
having count(*) > 2
) x
join flightleg y
on x.flno = y.flno
and (x.starter = y.depttime
or x.ender = y.depttime)
group by x.flno;
小提琴: http ://sqlfiddle.com/#!9/79640/1/0(TommCatt為提高效率提出了修改)
這不依賴於seq
中的每一次飛行升序之中。
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