如何简化下面的内部JOIN SQL查询

Question

我从不同的表中获取记录，并像这样将值连接起来，以便我可以显示Flight1、Flight2、Flight3和Flight4......作为列。既然我使用相同的条件，有没有办法简化这个查询?

SELECT b.BookingID
,(SELECT TOP 1 CONCAT(il.CCode,il.FlightNumber,';',dc.[Name])
FROM ILeg il
INNER JOIN PLeg pjl ON pjl.InventoryLegID = il.InventoryLegID
INNER JOIN PSegment pjs ON pjs.SegmentID = pjl.SegmentID
INNER JOIN BPassenger bp ON bp.PassengerID = pjs.PassengerID
INNER JOIN City dc ON dc.CityCode = il.DepartureStation
INNER JOIN City ac ON ac.CityCode = il.ArrivalStation
WHERE bp.BookingID =  b.BookingID AND il.CarrierCode = '12T'
ORDER BY il.STD
) AS Flight1
,(SELECT CONCAT((il.CCode,il.FlightNumber,';',dc.[Name]))
FROM ILeg il
INNER JOIN PLeg pjl ON pjl.InventoryLegID = il.InventoryLegID
INNER JOIN PSegment pjs ON pjs.SegmentID = pjl.SegmentID
INNER JOIN BPassenger bp ON bp.PassengerID = pjs.PassengerID
INNER JOIN City dc ON dc.CityCode = il.DepartureStation
INNER JOIN City ac ON ac.CityCode = il.ArrivalStation
WHERE bp.BookingID =  b.BookingID AND il.CarrierCode = '12T'
ORDER BY il.STD
OFFSET 1 ROWS
FETCH NEXT 1 ROWS ONLY) AS Flight2
,(SELECT CONCAT((il.CCode,il.FlightNumber,';',dc.[Name]))
FROM ILeg il
INNER JOIN PLeg pjl ON pjl.InventoryLegID = il.InventoryLegID
INNER JOIN PSegment pjs ON pjs.SegmentID = pjl.SegmentID
INNER JOIN BPassenger bp ON bp.PassengerID = pjs.PassengerID
INNER JOIN City dc ON dc.CityCode = il.DepartureStation
INNER JOIN City ac ON ac.CityCode = il.ArrivalStation
WHERE bp.BookingID =  b.BookingID AND il.CarrierCode = '12T'
ORDER BY il.STD
OFFSET 2 ROWS
FETCH NEXT 1 ROWS ONLY) AS Flight3
FROM Booking b
WHERE b.RecordLocator='1234'

谢谢

Answer 1

您可以在顶部使用CTE，而主查询可能如下图所示。

;with CTE as 
(SELECT CONCAT((il.CCode,il.FlightNumber,';',dc.[Name])) as DisplayName
FROM ILeg il
INNER JOIN PLeg pjl ON pjl.InventoryLegID = il.InventoryLegID
INNER JOIN PSegment pjs ON pjs.SegmentID = pjl.SegmentID
INNER JOIN BPassenger bp ON bp.PassengerID = pjs.PassengerID
INNER JOIN City dc ON dc.CityCode = il.DepartureStation
INNER JOIN City ac ON ac.CityCode = il.ArrivalStation
WHERE bp.BookingID =  b.BookingID AND il.CarrierCode = '12T'
ORDER BY il.STD),
SELECT b.BookingID
,(SELECT TOP 1 * from CTE) AS Flight1
,(SELECT TOP 1 * from CTE OFFSET 1 ROWS FETCH NEXT 1 ROWS ONLY) AS Flight2
,(SELECT TOP 1 * from CTE OFFSET 2 ROWS FETCH NEXT 1 ROWS ONLY) AS Flight3
FROM Booking b
WHERE b.RecordLocator='1234'