Comparing with NULL values

Question

CREATE TABLE `mycompare` (
  `name` varchar(100) default NULL,
  `fname` varchar(100) default NULL,
  `mname` varchar(100) default NULL,
  `lname` varchar(100) default NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

INSERT INTO `mycompare` VALUES('amar', 'ajay', 'shankar', NULL);
INSERT INTO `mycompare` VALUES('akbar', 'bhai', 'aslam', 'akbar');
INSERT INTO `mycompare` VALUES('anthony', 'john', 'Jim', 'Ken');
_____

SELECT * FROM mycompare WHERE (name = fname OR name = mname OR name = lname)
akbar   bhai    aslam   akbar

select * from mycompare where !(name = fname OR name = mname OR name = lname)
anthony john    Jim Ken

In the second select above, I expect the "amar" record as well because that name does not match with First, second or last name.

Answer 1

NULL values are omitted automatically if you do a value comparison (because NULL isn't a value). Your where clause basically means: Compare the values of the mentioned fields, if they have a value—otherwise false.

You'd have to include a separate check for NULL if you want those rows, too.

Answer 2

You cannot use relational operators with NULL. The only operators that work with NULL are IS NULL and IS NOT NULL.

Answer 3

You could probably get away with something like the following (assuming that mapping NULL to '' is not a problem):

SELECT * FROM mycompare 
WHERE (ifnull(name,'') = ifnull(fname,'') 
       OR ifnull(name,'') = ifnull(mname,'') 
       OR ifnull(name,'') = ifnull(lname,''));

select * from mycompare 
where !(ifnull(name,'') = ifnull(fname,'') 
        OR ifnull(name,'') = ifnull(mname,'')  
        OR ifnull(name,'') = ifnull(lname,''));