What is the size of NULL?

[UDIT]

Hi ,

I have a fundamental question :

What is the SIZE occupied by NULL in any oracle database . Is a null value same for a complete table?
If a null is given in the column of NUMBER datatype and another null in a column of VARCHAR2 datatype are they same?

A Unique key renders a column NOT to accept 2 same values , but the column can accept 2 NULL values , HOW is this possible??????

please help.

Thanks,
Udit.

 

[MikeLacey]

Sizes: Don't know -- carp might know.

Unique Keys: Yes, you can have more than one NULL in a unique index. If you don't want that to happen you can constrain the column(s) in that index to be NOT NULL.
Mike
michael.j.lacey@ntlworld.com

 

[vsundar2]

Hi

NULLS are stored in the database if they fall between columns which has data, with one byte to store the length of the column which is zero. If the null columns are in the trailing columns, then no storage is used. Based on this, I think there should be no difference between a NUMBER and VARCHAR2 datatypes being NULL.

Thanks
Vasu.