Search Postgresql Archives

What does Postgresql do when using CASE WHEN without ELSE?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]
  Powered by Linux