ROWGUIDCOL cannot be assigned to a column of a user-defined data type.
NOT NULL can be specified for computed columns only if PERSISTED is also specified.
If the new column allows null values and no default is specified, the new column contains a null value for each row in the table.
A column included in a primary key constraint, cannot be changed from NOT NULL to NULL. For more information about valid scale values, see Precision, Scale, and Length (Transact-SQL).
max Applies only to the varchar, nvarchar, and varbinary data types for storing 2^31-1 bytes of character, binary data, and of Unicode data.
Note The data type of a column of a partitioned table cannot be changed.
The data type of columns included in an index cannot be changed unless the column is a varchar, nvarchar, or varbinary data type, and the new size is equal to or larger than the old size.If the table is not in the current database or is not contained by the schema owned by the current user, the database and schema must be explicitly specified.ALTER COLUMN Specifies that the named column is to be changed or altered.NULL | NOT NULL Specifies whether the column can accept null values.Columns that do not allow null values can be added with ALTER TABLE only if they have a default specified or if the table is empty.For a list and more information, see Windows Collation Name (Transact-SQL) and SQL Server Collation Name (Transact-SQL).