Problem with empty string comparison

[Dušan Pavlica]

Hello,

I have upgraded MySQL from 4.0.7 to 4.1.9 (OS Win XP SP2) and now I have a problem with
empty string comparison.

Test case:

CREATE TABLE tb_test (
  t1 char(5) NOT NULL default '',
  t2 char(5) NOT NULL default ''
) ENGINE=MyISAM DEFAULT CHARSET=cp1250 COLLATE=cp1250_czech_cs;

INSERT INTO tb_test (t1, t2) VALUES('a', '');
INSERT INTO tb_test (t1, t2) VALUES('b', ' ');

SELECT t1, t2, length(t1), length(t2), t2 = '', t2 = ' ', t2 = '  ' FROM tb_test;

output:
t1   t2    length(t1)     length(t2)    t2 = ''    t2 = ' '    t2 = '  '
a           1                0                0          1           1  
b           1                0                0          1           1

I don't know why fields with zero length are not equal to empty string. If I change both
fields t1 and t2 to VARCHAR(5) situation is same.
Could someone help me to solve this out? Maybe I just missed some variable setting or
something like this.

Thanks in advance

Dusan Pavlica