Null size

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Uhway - 06 Feb 2005 19:24 GMT

I am creating a table with following fields:
CREATE TABLE Employee (
EmployeeID bigint NOT NULL,
EmpName Varchar(50),
EmpAge int,
ImageSize int,
EmpImage image,
Comments varchar (50) )

20% of the time all fields are populated. But rest of the time no image or
age is stored in the fields. So, when there is a null value in those
fields, what will be the size of the null value fields for calculating a row
size? On average the I can say the image size will be around 25K. I need
this information to calculate a space required for 25 million row table.

That's why I am particular about null(pointer?) value size.

Thanks
BVR

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Tomasz Borawski - 11 Feb 2005 13:39 GMT

Hi,

Each row in SQL Server has a fixed structure:
-    row header
-    null columns bit flags (typically 4 byte)
-    fixed length columns (like int, char)
-    variable length columns (like varchar)

If one of a bit is selected then a corresponding column has null value.

Typically, if you calculate required space, you do not have to worry about
null columns values. Instead of that, you should increase a total value by 10
percent.

Tomasz B.

> I am creating a table with following fields:
> CREATE TABLE Employee (
[quoted text clipped - 15 lines]
> Thanks
> BVR

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