SybaseBlog

There is a big difference between NULL and nothing. I will demonstrate one notable difference with a simple example.

First, create a table that allows NULLs and has a default value

create table test_table (col_a int default 0 null, col_b int null)
go

Now let's try inserting these rows:

1. A row where we assign neither value:

insert into test_table values ()
go

select * from test_table
go

col_a       col_b       
----------- ----------- 
          0        NULL 

Note: col_a got the default value, and col_b got NULL.
NULL is like the default value you get when you don't assign a default value to a column. Creating the column like this would be redundant: ... col_b int default null null)

2. A row where we assign NULL values:

insert into test_table (col_a, col_b) values (NULL, NULL)
go

select * from test_table
go

col_a       col_b       
----------- ----------- 
          0        NULL 
       NULL        NULL 

Note: Here, col_a got NULL. It did not use the default value.
Because a value was provided: NULL. NULL is a value.

Related Link: Earlier I wrote a blog about NULLs in Sybase:
http://sybasease.blogspot.com/2005/05/
nulls-in-sybase-ase.html

There are a lot of great resources on Sybase, and you can see some of them among my links. But there are some utilities/documents that are so valuable that I burn them on a CD and carry a copy with me.

1. SQSH

I have nothing against isql. But SQSH (SQL-Shell, developed by Scott Gray) allows you to edit previous statements (even far back in your history), use variables, among many other things. It's hard to use ISQL when I could be using SQSH.

http://www.sqsh.org/

2. Sybooks

Obviously I need the ultimate reference. Sybooks is the quickest and easiest way to look up error messages and commands. I always install my own copy so I don't have to rely on Internet access.

http://sybooks.sybase.com/

3. SybPerl

For advanced database work, it is handy to use Perl to write scripts. Because it is quick and easy to write, and can be used on every O/S. SybPerl is a set of libraries, developed by Michael Peppler, of the most common tasks.

http://www.peppler.org/~mpeppler/

4. Sybase Product Manuals

These are more than references (which you use Sybooks for anyway). You want the following (at least):
- The Quick Reference Guide
- The System Tables Diagram
- The Glossary (trust me!)
- The Performance and Tuning Guide
- The Reference Manuals (all 4, including building blocks, commands, procedures and tables)
- System Administration Guide
- Transact-SQL User's Guide
- Troubleshooting and Error Messages Guide
- Utility Guide

http://sybooks.sybase.com/asg1250e.html

5. Various Utility Procs

Everyone has their own collection of handy utilities, procedures and scripts. If you don't, you can start building your library based on those of others. I heartily recommend starting with Ed Barlow and Todd Boss and take it from there. You'll keep most of your library on a memory stick because you'll be constantly tweaking them, but your core procedures belong on the disk.

I'm interested in hearing what you felt I may have left out. Please leave comments!