It seems that you don't know what the NULL values are :) Yes, in the case when the column value is declared as NOT NULL, COUNT(value) is equivalent to COUNT(*).

But look at the example:

CREATE TEMPORARY TABLE testnull0 (
  id INT NOT NULL auto_increment,
  value VARCHAR(100),
  PRIMARY KEY(id)
)
ENGINE=MyISAM;

INSERT INTO testnull0 (id, value) VALUES (1, 'hello'), (2, 'googbye'),
+ (3, NULL);

SELECT COUNT(id), COUNT(value), COUNT(*) FROM testnull0;

[download]
Being processed by MySQL (you must specify your DB name, of course), it prints: 
+-----------+--------------+----------+
| COUNT(id) | COUNT(value) | COUNT(*) |
+-----------+--------------+----------+
|         3 |            2 |        3 |
+-----------+--------------+----------+

[download]
Got the idea? You cannot rely on the suggestion that the value column is declared as NOT NULL, if you did not create the table yorself :) while COUNT(*) always works as expected.

It's REALLY off-topic here, but i think that answering an OT question wrong is worse than answering it right—and even worse than not answering it at all.

In reply to Re^4: Perl and MySQL: Get number of rows affected by Ieronim
in thread Perl and MySQL: Get number of rows affected by Spidy

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