特定列的mySQL，WHERE语句

Question

我必须选择从'München'到'Düsseldorf'的所有航班并返回。表flightexecutions包含查找正确航班的信息。

我的陈述如下所示，我只能选择FlightNo和机场“来自”。

我不知道如何设置我的SELECT语句以获得包含FlightNo，from和to列的所需输出。

<pre id="pre"></pre>

--1)statements works correct, returns all FlightNo and origin "from"
SELECT flx.FlightNo, air.AirportName as `from`, air.AirportName as `to`
FROM flightexecution as flx, airport.airport as air
WHERE flx.ICAO_Code_Origin = air.ICAO_Code and (air.AirportName LIKE 'München (Franz Josef Strauß)'
OR air.AirportName LIKE 'Düsseldorf International');

--2)returns all flightNo and destination "to"
SELECT flx.FlightNo, air.AirportName as `to`
FROM flightexecution as flx, airport.airport as air
WHERE flx.ICAO_Code_Destination = air.ICAO_Code and (air.AirportName LIKE 'München (Franz Josef Strauß)'
      OR air.AirportName LIKE 'Düsseldorf International');

output1):

    FlightNo | from 
    -----------------
             |   

output2):

    FlightNo | to 
    -----------------
             |    




desired output:

FlightNo | from | to 
-------------------------
         |      |  

Answer 1

这个怎么样：

WHERE (flx.ICAO_Code_Origin = air.ICAO_Code 
  and (air.AirportName LIKE 'München (Franz Josef Strauß)' 
    OR air.AirportName LIKE 'Düsseldorf International')) 
  AND (flx.ICAO_Code_Destination = air.ICAO_Code 
  and (air.AirportName LIKE 'München (Franz Josef Strauß)' 
    OR air.AirportName LIKE 'Düsseldorf International'));

Answer 2

应该这样做;它将所有flightexecutions独立地连接到它们的起始和目的地机场，然后使用WHERE条件将连接结果过滤到只有那些具有所需端点的那些。

SELECT fx.FlightNo, o.AirportName AS `from`, d.AirportName AS `to`
FROM flightexecution AS fx
INNER JOIN airport AS o ON fx.ICAO_Code_Origin = o.ICAO_Code
INNER JOIN airport AS d ON fx.ICAO_Code_Destination = d.ICAO_Code
WHERE (o.AirportName = 'München (Franz Josef Strauß)' AND d.AirportName = 'Düsseldorf International')
   OR (d.AirportName = 'München (Franz Josef Strauß)' AND o.AirportName = 'Düsseldorf International')

旁注：由于MySQL处理OR条件的方式（差）;如果数据库很大，那么通过UNIONing这个查询的两个版本（一个包含WHERE条件的每个OR部分）可能会有更好的性能。

Answer 3

SELECT flx.FlightNo AS flightname, air.AirportName as从, airTo.AirportName as到FROM flightexecution as flx, airport.airport as air,airport.airport as airTo, flightexecution as flxFrom WHERE (flx.ICAO_Code_Origin = air.ICAO_Code and (air.AirportName LIKE 'München (Franz Josef Strauß)'OR air.AirportName LIKE 'Düsseldorf International')) AND (flxFrom.ICAO_Code_Destination = airTo.ICAO_Code and (airTo.AirportName LIKE 'München (Franz Josef Strauß)' OR airTo.AirportName LIKE 'Düsseldorf International'));

试试这个