title: Declare variable set = select
body: <p>How do I declare a variable for used in a PostgreSQL 9.3 query?</p>
  <pre><code>CREATE or replace FUNCTION public.test()
    returns int4
  AS
  $BODY$
  DECLARE    
      cod_process bigint :=30001;
      cod_instance bigint ;
      utc_log timestamp without time zone := localtimestamp;
      cod_log_type varchar(100) :='information ';
      txt_log_text varchar(100):= 'start process';
      txt_log varchar(100):= txt_log_text||'_'||cod_process;
      set cod_instance= select max(cod_instance) as cod_instance from public.instance where public.instance.cod_process=cod_process;    
  BEGIN  
      INSERT INTO public.log (cod_process, cod_instance, utc_log,cod_log_type,txt_log)
      VALUES (cod_process, cod_instance, utc_log,cod_log_type,txt_log );
      RETURN 11;
  END;
  $BODY$ LANGUAGE 'plpgsql';
  </code></pre>
  <blockquote>
  <pre><code>ERROR: type &quot;cod_instance&quot; does not exist
  SQL state: 42704
  Character: 383
  </code></pre>
  </blockquote>