SQL : Test if a column has the "Not Null" property

Is there a simple que开发者_运维百科ry to return whether a specific column allows nulls?

I want to change this as part of a DB upgrade script.

Alternatively, is it better to just change it, even if its already set?

Edit : This is for SQL Server (needs to support 2000 or later)

Any particular RDBMS?

In SQL Server

use master

SELECT COLUMNPROPERTY( OBJECT_ID('dbo.spt_values'),'number','AllowsNull')

Or (more standard)

select IS_NULLABLE 
from INFORMATION_SCHEMA.COLUMNS 
where TABLE_SCHEMA='dbo' 
      AND TABLE_NAME='spt_values' 
      AND COLUMN_NAME='number'