Updating one table from another sql server
NOT NULL can be specified in ALTER COLUMN only if the column contains no null values.
The null values must be updated to some value before the ALTER COLUMN NOT NULL is allowed, for example: When you create or alter a table with the CREATE TABLE or ALTER TABLE statements, the database and session settings influence and possibly override the nullability of the data type that is used in a column definition.
The modified column cannot be any one of the following: Some data type changes may cause a change in the data.
For example, changing an nchar or nvarchar column to char or varchar may cause the conversion of extended characters.
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.
If the new column allows null values and a default definition is added with the new column, WITH VALUES can be used to store the default value in the new column for each existing row in the table.
If not specified, the column is assigned the default collation of the database.