Question

I have aSQLite3 database with three tables. Sample data looks like this:

Original

id    aName  code 
------------------
1     dog     DG  
2     cat     CT  
3     bat     BT  
4     badger  BDGR
...   ...     ... 

Translated

id   orgID   isTranslated  langID   aName     
----------------------------------------------
1     2           1         3       katze     
2     1           1         3       hund      
3     3           0         3       (NULL)    
4     4           1         3       dachs     
...   ...         ...       ...     ...        

Lang

id Langcode
-----------
1    FR  
2    CZ
3    DE
4    RU
...  ...

I want to select all data from Original and Translated in way that result would consist of all data in Original table, but aName of rows that got translation would be replaced with aName from Translated table, so then I could apply an ORDER BY clause and sort data in the desired way.

All data and table designs are examples just to show the problem. The schema does contain some elements like an isTranslated column or translation and original names in separate tables. These elements are required by application destination/design.

To be more specific this is an example rowset I would like to produce. It’s all the data from table Original modified by data from Translated if translation is available for that certain id from Original.

Desired Result

id    aName  code    isTranslated
---------------------------------  
1     hund     DG         1
2     katze    CT         1
3     bat      BT         0
4     dachs    BDGR       1
...   ...      ...        ...

Answer 1

This is a typcial application for the CASE expression:

SELECT Original.id,
       CASE isTranslated
         WHEN 1 THEN Translated.aName
         ELSE        Original.aName
       END AS aName,
       code,
       isTranslated
FROM Original
JOIN Translated ON Original.id = Translated.orgID
WHERE Translated.langID = (SELECT id FROM Lang WHERE Langcode = 'DE')

If not all records in Original have a corresponding record in Translated, use LEFT JOIN instead.

If untranslated names are guaranteed to be NULL, you can just use IFNULL(Translated.aName, Original.aName) instead.