SQL query on a condition - sql

Question

I'm writing a query to retrieve translated content. I want it so that if there isn't a translation for the given language id, it automatically returns the translation for the default language, with Id 1.
select Translation.Title
,Translation.Summary
from Translation
where Translation.FkLanguageId = 3
-- If there is no LanguageId of 3, select the record with LanguageId of 1.
I'm working in MS SQL but I think the theory is not DBMS-specific.
Thanks in advance.

Answer 1

This assumes one row per Translation only, based on how you phrased the question. If you have multiple rows per FkLanguageId and I've misunderstood, please let us know and the query becomes more complex of course
select TOP 1
Translation.Title
,Translation.Summary
from
Translation
where
Translation.FkLanguageId IN (1, 3)
ORDER BY
FkLanguageId DESC
You'd use LIMIT in another RDBMS

Answer 2

Assuming the table contains different phrases grouped by PhraseId
WITH Trans As
(
select Translation.Title
,Translation.Summary
,ROW_NUMBER() OVER (PARTITION BY PhraseId ORDER BY FkLanguageId DESC) RN
from Translation
where Translation.FkLanguageId IN (1,3)
)
SELECT *
FROM Trans WHERE RN=1

Answer 3

This assumes the existance of a TranslationKey that associates one "topic" with several different translation languages:
SELECT
isnull(tX.Title, t1.Title) Title
,isnull(tX.Summary, t1.Summary) Summary
from Translation t1
left outer join Translation tX
on tx.TranslationKey = t1.Translationkey
and tx.FkLanguageId = #TargetLanguageId
where t1.FkLanguageId = 1 -- "Default

Answer 4

Maybe this is a dirty solution, but it can help you
if not exists(select t.Title ,t.Summary from Translation t where t.FkLanguageId = 3)
select t.Title ,t.Summary from Translation t where t.FkLanguageId = 1
else
select t.Title ,t.Summary from Translation t where t.FkLanguageId = 3

Answer 5

Since your reference to pastie.org shows that you're looking up phrases or specific menu item names in a table I'm going to assume that there is a phrase ID to identify the phrases in question.
SELECT ISNULL(forn_lang.Title, default_lang.Title) Title,
ISNULL(forn_lang.Summary, default_lang.Summary) Summary
FROM Translation default_lang
LEFT OUTER JOIN Translation forn_lang ON default_lang.PhraseID = forn_lang.PhraseID AND forn_lang.FkLanguageId = 3
WHERE default_lang.FkLanguageId = 1