Thread

1. Weirdness with =?

   Christopher Kings-Lynne <chriskl@familyhealth.com.au> — 2006-01-30T08:44:21Z

   I had this code in a script:
   
   UPDATE food_foods SET included=true WHERE verification_status = 'I';
   UPDATE food_foods SET included=false WHERE verification_status IS NULL;
   
   I tried replacing it with:
   
   UPDATE food_foods SET included=(verification_status = 'I');
   
   However, that set included to true only where verification_status=I, it 
   didn't set false at all.
   
   Why doesn't this work?
   
   Chris
   
   
   
   

2. Re: Weirdness with

   Martijn van Oosterhout <kleptog@svana.org> — 2006-01-30T09:30:18Z

   On Mon, Jan 30, 2006 at 04:44:21PM +0800, Christopher Kings-Lynne wrote:
   > I had this code in a script:
   > 
   > UPDATE food_foods SET included=true WHERE verification_status = 'I';
   > UPDATE food_foods SET included=false WHERE verification_status IS NULL;
   > 
   > I tried replacing it with:
   > 
   > UPDATE food_foods SET included=(verification_status = 'I');
   
   (NULL = 'I')   is null, not false. It will simply set rows where
   verification_status is NULL to NULL also.
   
   Perhaps you mean IS NOT DISTNCT FROM or something similar?
   
   Have a nice day,
   -- 
   Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
   > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
   > tool for doing 5% of the work and then sitting around waiting for someone
   > else to do the other 95% so you can sue them.
   

3. Re: Weirdness with =?

   Tom Lane <tgl@sss.pgh.pa.us> — 2006-01-30T15:00:20Z

   Christopher Kings-Lynne <chriskl@familyhealth.com.au> writes:
   > I tried replacing it with:
   > UPDATE food_foods SET included=(verification_status = 'I');
   > However, that set included to true only where verification_status=I, it 
   > didn't set false at all.
   
   You'd have gotten NULL, not FALSE, at the rows where verification_status
   is NULL.
   
   You could try coalesce, or "(verification_status = 'I') IS TRUE", to
   get something that returns false instead of null.
   
   			regards, tom lane