Date: Sun, 16 Apr 2000 23:03:12 +0200
From: Ivo Simicevic <ivo@ultra.hr>
To: pgsql-interfaces@postgreSQL.org
Subject: Re: a couple of newbie question
Message-ID: <20000416230312.A1117@ultra.hr>
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On Sun, Apr 16, 2000 at 11:57:38AM -0700, Matthew Denny wrote:
> 
> I know this question is probably fairly elementary, but I could not
> find the answer in the docs or mailing list archives.  How does one handle
> NULL values in the embedded SQL interface?  For example, if I have a
> statement:
> 
> exec sql insert into test_table values(:foo, :x, :y)
> 
> and foo represents a CHAR attribute (represented by a string in C) that I
> want to set to NULL, how do I go about doing this?  

There are two ways :

  exec sql insert into test_table values (NULL,:x,:y)    or more properly

define indicator variable in DECLARE section and use it to insert null value
e.g.

  EXEC SQL BEGIN DECLARE SECTION;
  char foo[10];
  int x;
  int y;
  int indicator;
  EXEC SQL END DECLARE SECTION;
.....
  indicator=-1;
  EXEC SQL INSERT INTO test_table VALUES (:foo:indicator,:x,:y);


> Similarly, how do
> I tell that a value put into a variable by a fetch call is NULL or
> not?  
> 

  You can do it the same way:

  EXEC SQL SELECT foo,x,y
           INTO :foo:indicator,:x,:y
           ......

  and then check for indicator value.


GL

Ivo.