Question

Advert table, Newspaper column takes integer value.

  Newspaper
      1
      2
      3

Newspaper table like this

NewspaperName UnitPrice
 A              12.00
 B              11.00
 C              5.00

Query;

select 
    case 
       when a.Newspaper = 1 then 'A' 
       when a.Newspaper = 2 then 'B' 
       when a.Newspaper = 3 then 'C'
       when a.Newspaper = 4 then 'D' 
       else 'Empty' 
    end as NewspaperName 
from Advert 
left join...

It’s the little foolish. But I want to left join Advert table to Newspaper. How to join this?

Answer 1

Just use your “translation query” as a subquery:

SELECT AdvertTranslated.whatever1, Newspaper.whatever2 FROM
    (select case when a.Newspaper = 1 then 'A'
                 when a.Newspaper = 2 then 'B'
                 when a.Newspaper = 3 then 'C' 
                 when a.Newspaper = 4 then 'D'
                 else 'Empty' 
            end as NewspaperName,
            whatever1
       from Advert) AdvertTranslated
    LEFT JOIN Newspaper ON AdvertTranslated.NewspaperName = Newspaper.NewspaperName