Perhaps an extra byte is automatically reserved, not only for a null/not null status bit, but also for other internal use - eg; a 'row changed' bit, etc.
I did a quick test:
mysql> create table t2 (c1 varchar(255));
Query OK, 0 rows affected (0.00 sec)
mysql> insert into t2 values ('s');
Query OK, 1 row affected (0.00 sec)
And this gave table status of
Name: t2
Type: MyISAM
Row_format: Dynamic
Rows: 1
Avg_row_length: 20
Data_length: 20
Max_data_length: 4294967295
Index_length: 1024
Data_free: 0
Auto_increment: NULL
so obviously the avg_row_length includes extra bytes for mysql internal info.
Learn something every day!
-steve
At 1:03 PM +0100 1/15/03, you wrote:
Steve,I believe there is an extra byte for the 'null' flag; if you declare this column to be NOT NULL, I'll bet the avg length will be 10.nice bet, but you lose <g>:mysql> DESCRIBE mynotnullisam; +-------+----------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+----------+------+-----+---------+-------+ | col | char(10) | | | | | +-------+----------+------+-----+---------+-------+ 1 row in set (0.16 sec) mysql> SHOW TABLE STATUS LIKE 'mynotnullisam'; +---------------+--------+------------+------+----------------+--------- ----+ | Name | Type | Row_format | Rows | Avg_row_length | Data_length | +---------------+--------+------------+------+----------------+--------- ----+ | mynotnullisam | MyISAM | Fixed | 3 | 11 | 33 | +---------------+--------+------------+------+----------------+--------- ----+
-- +------------------------------------------------------------------------+ | Steve Edberg [EMAIL PROTECTED] | | University of California, Davis (530)754-9127 | | Programming/Database/SysAdmin http://pgfsun.ucdavis.edu/ | +------------------------------------------------------------------------+ | SETI@Home: 1001 Work units on 23 oct 2002 | | 3.152 years CPU time, 3.142 years SETI user... and STILL no aliens... | +------------------------------------------------------------------------+ --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
