Add non-nullable columns to an existing table in SQL server?

Question

I already have a table which consists of data. I need to alter the table to add two new columns which are not null. How can I do that without losing any existing data?

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Here's what I tried (via right-clicking the table and selecting Design):

1. Added new columns 'EmpFlag' (bit, null), 'CreatedDate' (datetime, null)

2. Updated 'EmpFlag' column in the table, to have some valid values. (Just wanted to work on one field, so I didn't update 'CreatedDate' field)

3. Now right clicked table, design, and made it not null.

When I tried to save, this error message appeared:

Saving changes is not permitted. The changes you have made require the following tables to be dropped and re-created.

Answer 1

You just set a default value in the new columns and that will allow you to add them.

alter table table_name     add column_name datetime not null        constraint DF_Default_Object_Name default (getdate()) 

or this one for a varchar field.

alter table table_name     add column_name varchar(10) not null        constraint DF_Default_Object_Name default ('A') 

You can also drop the default if you do not need it after you added the column.

alter table table_name     drop constraint DF_Default_Object_Name