Question

我有两个表在SQLServer2008中命名StationTabs和Links。

StationTabs
------------
StationId(int)
Longitude(float)
Latitude(float)


Links
----
id(int)
StationStart(int)
StationEnd(int)

StationStart和StationEnd是StationId的外键。我应该使用相同的查询获取StationStart和StationEnd的经度和纬度值。我尝试过这样的事情;

Select Longitude,Latitude
From StationTabs, (Select * From Links ) As ST1, (Select * From Links) As ST2
Where ST1.StationStart=StationTabs.StationId  AND ST2.StationEnd=StationTabs.StationId;

此语句仅返回StationEnd的经度和纬度值。有人可以帮忙吗？

例如;

StationId = 1, Longitude = 35,18, Latitude = 37,01
StationId = 2, Longitude = 36,43, Latitude = 38,88

在链接表中;

id = 3, StationStart = 2 , StationStart = 1

结果，我必须得到

的值

lonStart=36,43 and latStart = 38,88
lonEnd=35,18 and latEnd=37,01

Answer 1

这应该有效：

SELECT Longitude, 
       Latitude 
FROM   StationTabs st
INNER JOIN Links lStart
    ON st.StationId = lStart.StationStart
INNER JOIN Links lEnd
    ON st.StationId = lEnd.StationEnd

如果其中一个（或两者）都可以为null，但您想要包含此记录，则应使用LEFT OUTER JOIN代替。

Answer 2

您的子选择完全没有意义，应该写成常规的JOIN操作：

SELECT Longitude, Latitude, ST1.id, ST2.id
FROM StationTabs
LEFT JOIN Links AS ST1 on StationTabs.StationID = ST1.StationStart
LEFT JOIN Links AS ST2 on StationTabs.StationID = ST2.StationEnd

Answer 3

如果您想要获取每个Links条目的开始和结束纬度/经度值，那么您对错误表格的引用加倍：

SELECT
    ST1.Longitude as StartLong,
    ST1.Latitude as StartLat,
    ST2.Longitude as EndLong,
    ST2.Latitude as EndLat,
    l.ID as LinkID
FROM
   Links l
      inner join
   StationTabs ST1
      on
          l.StationStart = ST1.StationId
      inner join
   StationTabs ST2
      on
          l.StationEnd = ST2.StationId

Answer 4

Select Long,Lat From StationTabs where (StationId  IN (Select StationStart From Links) OR StationId IN (select StationEnd from Links))

正确加入SQL中的表

4 个答案: