Apologies, I found the answer in the documentation: http://www.postgresql.org/docs/9.0/static/functions-conditional.html says: "If the ELSE clause is omitted and no condition is true, the result is null."
Best regards Seref On Tue, Feb 12, 2013 at 10:39 AM, Seref Arikan < serefari...@kurumsalteknoloji.com> wrote: > Greetings, > I want to use CASE WHEN to make sure that I don't try to call a function > on a row that does not exist. This is used within a WHERE statement as > follows (without the function call I've mentioned); > > WHERE > CASE WHEN EXISTS(SELECT ATRNODE.featuremappingid from ELEMENT1, > ATRNODE where ELEMENT1.pathstring || '/' || 'name/value' = > ATRNODE.pathstring) > THEN > ( ELEMENT1.pathstring || '/' || 'name/value' = ATRNODE.pathstring > and > ATRNODE.valstring = 'Måltillstånd' --this will be where the > function is going to be used > ) > ELSE > ELEMENT1.id = -1291927189371983619872981729 > END > > The overall mechanism lets me apply a constraint so that if a row does not > exist, the query returns no results, without attempting to process > ATRNODE.valstring value (which represents more complicated info that will > exist in the row in other cases) > The thing is, when I omit the ELSE, the query still returns no results if > the row does not exist. It is as if an ELSE statement is added with an > impossible constraint, just like the one I'm explicitly providing. > I'm keeping the ELSE so that I explicitly introduce a where statement > that will not correspond to any rows, but what is happening when I omit > ELSE, so that the query still functions as it should? > > Best regards > Seref > >
