如何將表的鏈接列轉換為 SQL 中的行？

Question

我有一個表如下：

ID | Fileid1 | Fileid2 | Fileid3 | LanguageID1 | LanguageID2 | LanguageID3
---------------------------------------------------------------------------
1  | 123     | 256     |         | a12         | a23         | 
2  | 124     |         |         | a12         |             |

這里LanguageID1對應Fileid1 ， LanguageID2對應Fileid2等等。

我想將其轉換為以下內容：

ID | Field | LangaugeID
1  | 123   | a12
2  | 256   | a23
3  | 124   | a12

我嘗試在這兩個字段上使用UNPIVOT ，但它給出了所有列之間的關系。 這樣做的方法應該是什么？

Answer 1

您可以使用聯合：

select row_number() over(order by ID, Fileid) as ID,
Fileid,
LanguageID 
from
(select ID, Fileid1 as Fileid, LanguageID1 as LanguageID from table_name
union all select ID, Fileid2 as Fileid, LanguageID2 as LanguageID from table_name
union all select ID, Fileid3 as Fileid, LanguageID3 as LanguageID from table_name) t
where Fileid is not null

小提琴

Answer 2

你可以試試：

select id, Fileid, LanguageID
from (
        select id,fileid1 as Fileid,LanguageID1 as LanguageID 
        from  my_table 
      union all 
        select id,fileid2 as Fileid ,LanguageID2 as LanguageID
        from  my_table 
      union all 
       select id,fileid3 as Fileid ,LanguageID3 as LanguageID
       from  my_table 
       ) as t1
where concat_ws('',Fileid,LanguageID) !=''   

演示