Question

表一

ID  LinkId
1     0
2     1
3     2

表2

ID  IntersectionID  X   Y
1       5          100  200
2       6          300  400
3       7          800  500

表3

ID  IntersectionID  Sequence_number linkId  LinkDirection
1        5              0             0       Positive
1        5              1             1       negative
2        6              0             0       negative

我想要一个查询给我以下

ID  LinkId  X(start) Y(Start) X(End) Y(End)
1      0      100     200      300    400

对于表1中的每一行，从表3中获取其IntersectionID（使用链接字段），（链接方向 - 正表示起点，负表示终点）。然后转到表2并填充x，y值。

帮助我实现它。

尝试了这个查询。无法得到它。

select r1.id id, r1.linkid base_link_id, r2.X startX,r2.Y startY from  table1 r1, table2 r2 
  where  startX = (select X from table2 where id = r1.id and intersectionId =
  (select intersectionId from table3 where id = r1.id and linkId= r1.linkid  and LinkDirection = positive)) and startY
  = (select Y from table2 where id = r1.id and intersectionId  = 
  (select intersectionId from table3 where id = r1.id and linkId= r1.linkid  and LinkDirection = negative));

Answer 1

使用此查询，您应该可以执行此操作。

注意LinkDirection的文字。

SELECT 
    t1.ID
    ,t1.LinkId
    ,t2_start.X as X_Start
    ,t2_start.Y as Y_Start
    ,t2_end.X as X_End
    ,t2_end.Y as Y_End
FROM    
    table1 t1
    LEFT JOIN table3 t3_start
        on t1.linkId = t3_start.linkId  
        and t3_start.LinkDirection = 'Positive'
    LEFT JOIN table2 t2_start
        on t2_start.IntersectionID = t3_start.IntersectionID 

    LEFT JOIN table3 t3_end
        on t1.linkId = t3_end.linkId  
        and t3_end.LinkDirection = 'negative'
    LEFT JOIN table2 t2_end
        on t2_end.IntersectionID = t3_end.IntersectionID

如果table2中没有行，您将在t2_start.X t2_start.Y t2_end.X t2_end.Y中获得空字段。您可以使用

将其更改为0或-1

CASE WHEN t2_start.X is not null THEN t2_start.X ELSE -1 END

Answer 2

如果您需要澄清，希望以下查询有用。请问

SELECT ID,LinkID,MAX(StartX) AS StartX ,MAX(Starty) AS StartY,
MAX(EndX) AS EndX,MAX(EndY) AS EndY FROM
(
  SELECT a.ID,a.LinkID,X as StartX,Y as StartY,null as EndX,null as EndY  
   FROM 
          table1 a JOIN table3 b 
               ON a.Linkid=b.Linkid 
          JOIN table2 c 
               ON b.id=c.id WHERE LinkDirection='Positive'
  UNION ALL
  SELECT a.ID,a.LinkID,null as StartX,null as StartY,X as EndX,Y as EndYY 
   FROM 
          table1 a JOIN table3 b 
                ON a.Linkid=b.Linkid 
          JOIN table2 c 
                ON b.id=c.id WHERE LinkDirection='Negative'
) t
GROUP BY ID,LinkID

这将返回

ID  LinkID  StartX  StartY   EndX    EndY
1     0      100     200     300     400
2     1      NULL    NULL    100     200

无法创建SQL Join查询

2 个答案: