Fixed bug #530

State default value for `AllowNull` SQLColumn property in README.

Author: ckadluba

README.md

@@ -383,7 +383,7 @@ Numeric types use the default precision and scale. For numeric types, you are re
 
 ### AllowNull
 
-Determines whether or not the column can store SQL `NULL` values. Some of the other features like `PrimaryKey` have related restrictions, and some of the Standard Columns impose restrictions (for example, the `Id` column never allows nulls).
+Determines whether or not the column can store SQL `NULL` values. The default is true. Some of the other features like `PrimaryKey` have related restrictions, and some of the Standard Columns impose restrictions (for example, the `Id` column never allows nulls).
 
 ### DataLength