[SQL] Some more weird NULL behavior

[Ludwig Lim]

Hi:

  I tried the following:
  CREATE TABLE x(
       a  NUMERIC(5,0),
       b  VARCHAR(5)
  );

  CREATE TABLE y(
       a  INTEGER,
       b  VARCHAR(5)
  );

  INSERT INTO x(b) VALUES ('LUDZ');
  INSERT INTO y(b) VALUES ('TEST');

  SELECT x.b,y.b FROM x,y WHERE x.a=y.a 
  returns zero rows.

  However:
  SELECT b FROM x WHERE a IS NULL returns 'LUDZ'
  SELECT b from y WHERE a IS NULL returns 'TEST'

  I also tried
  SELECT x.b,y.b
  FROM x,y
  WHERE x.a = CAST(y.a AS INTEGER);

  But it also returns zero rows.


Thank you in advance,
ludwig.
  

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