On Nov 27, 2007, at 8:47 PM, Michael Glaesemann wrote:


On Nov 27, 2007, at 21:04 , Gera Mel Handumon wrote:

I encounter an error if i use NULLIF with timestamp with time zone.
eq. dbtime=nullif(mytime,'')

i want to null the value of field DBTIME if the variable mytime=" "

DBTIME ="timestamp with time zone" datatype

error: column DBTIME is of type timestamp with time zone but expression is of type text.

I believe the reason is that '' is not a valid timestamp value: think of it this way:

IF mytime = '' THEN
  mytime := NULL;
END IF;

The first thing it needs to do is compare the mytime value with ''. As '' is not a valid timestamp value, it may be casing mytime to text. You'll run into problems if you're assigning a text value to a timestamp field (which happens after the initial comparison--and the cast--are done.)

I think you may need to handle this is you middleware, or handle the IF THEN explicitly in a function. Maybe CASE would work:

CASE WHEN mytime = '' THEN NULL
     ELSE CAST(mytime AS TIMESTAMP)
    END


Why not just:

UPDATE table
SET mytime=NULL
WHERE mytime='';

Erik Jones

Software Developer | Emma®
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