为什么这个联盟没有给我两列？

Question

我想在连接的输出中有两列。我只得到一个，即storeID。 StoreComponentID不在那里。

Answer 1

如果你想要两列你需要声明两列

SELECT column1, NULL as column2 -- even when Table1 doesnt have column2
FROM Table1
UNION 
SELECT NULL as column1, column2 -- even when Table2 doesnt have column1
FROM Table2

现在，如果你想并排进行某种合并。

WITH idA as (
     SELECT StoreComponentID,
            ROW_NUMBER() OVER (ORDER BY StoreComponentID) as rn
     FROM StoreComponent
), idB as (
     SELECT StoreID
            ROW_NUMBER() OVER (ORDER BY StoreID) as rn
     FROM Store
)
SELECT idA.StoreComponentID, 
       idB.StoreID
FROM idA 
FULL JOIN idB
  ON idA.rn = idB.rn

Answer 2

我找到了一个简单的解决方案：

select S.storeid as sID, SC.storecomponentid as SCID from tstore as S, tstorecomponent as SC