update null fields, PostgreSQL

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create table tableA (company varchar(20)  NOT NULL,option varchar(20), new bool, gap bool, ccc bool);
create table tableB (company varchar(20)  NOT NULL,option varchar(20), new bool, gap bool, ccc bool);

ALTER TABLE tableA
    ADD CONSTRAINT tableA_uq
    UNIQUE (company, option);
    
INSERT INTO tableA(company, option, new, gap, ccc)
VALUES
 ('a', 'd','f','t',null),
 ('a', 'g','f',null,'f'),
 ('c', 'g','f',null,'f');
 
 INSERT INTO tableB(company, option, new, gap, ccc)
VALUES
 ('a', 'd','f','t','f'),
 ('a', 'g','f',null,'f'),
 ('c', 'g','f',null,'f');
  
 SELECT * FROM tableA;
 SELECT * FROM tableB;

DELETE FROM tableA a
WHERE  EXISTS (
   SELECT FROM tableB b
   WHERE a.company = b.company
   )
AND    NOT EXISTS (
   SELECT FROM tableB b
   WHERE (a.company, a.option) IS NOT DISTINCT FROM
         (b.company, b.option)
   );
 
 /**INSERT INTO tableA (company, option, new, gap, ccc) 
   SELECT company, option, new, gap, ccc
   FROM   tableB
 ON CONFLICT (company, option) 
 DO update
   set new= EXCLUDED.new,
   gap = excluded.gap,
   ccc = excluded.ccc
   
 WHERE 
      ??**/
  
SELECT * FROM tableA;


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