Hi!
----- Original Message -----
From: ""Martijn Tonies"" <[EMAIL PROTECTED]>
Newsgroups: mailing.database.myodbc
Sent: Thursday, March 16, 2006 8:59 PM
Subject: Re: NULL columns
When doing an insert using NULL in the insert request,
what really is being written in the column?
Is the word NULL being written?
Is any real space being consumed?
In the cases that you really want to store NULL ;-)
No, it's not the word "null".
Of course space is consumed.
How much depends, see, for example:
http://dev.mysql.com/doc/refman/5.0/en/static-format.html
or
http://dev.mysql.com/doc/refman/5.0/en/dynamic-format.html
This is for MyISAM, InnoDB behaves differently.
InnoDB's old table format in 4.1 and earlier kept a fixed-length column the
same length even when the value NULL was stored. That, of course, wasted a
lot of space. The advantage was less fragmentation in updates.
InnoDB's new table format in 5.0 does not use any space to store a NULL. The
column itself needs one bit to indicate whether the value is NULL or not.
Martijn Tonies
Database Workbench - development tool for MySQL, and more!
Upscene Productions
http://www.upscene.com
My thoughts:
http://blog.upscene.com/martijn/
Database development questions? Check the forum!
http://www.databasedevelopmentforum.com
Best regards,
Heikki
Oracle Corp./Innobase Oy
InnoDB - transactions, row level locking, and foreign keys for MySQL
InnoDB Hot Backup - a hot backup tool for InnoDB which also backs up MyISAM
tables
http://www.innodb.com/order.php
--
MySQL General Mailing List
For list archives: http://lists.mysql.com/mysql
To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
