Still returning NULL when default value added - sql

Question

I'm trying to replace NULL with a default value of 'NO' but even when I execute it, it still displays NULL when I try to view the data. I've already tried dropping the constraint on the column, but it did not work
/*------------------------
use AuntieB
--alter table charity
-- add STORE char(10);
--update charity
--set STORE = 'YES'
--where Name = 'Salvation Army' or Name = 'Mother Wattles' or Name = 'Fresh Start Charity'
alter table charity
add default 'No' for STORE;
select * from charity
------------------------*/
CharityID Name Address City State Zip Phone ContactID STORE
----------- -------------------- ------------------------------ ------------------------------ ----- ---------- ------------ ----------- ----------
1000 St. Francis Home 45875 West. Hill St. Utica MI 48045 586-795-3486 1025 NULL
1001 Helping Hands 98563 Stadium Detriot MI 48026 313-978-6589 1030 NULL
1002 Boy Scouts 1155 E. Long Lake Rd Troy MI 48085 248-253-9596 1036 NULL
1003 Focus Hope 54362 Grand River Detroit MI 48312 313-478-7895 1041 NULL
1004 Fresh Start Charity 12569 Gratiot Ave. Roseville MI 48084 555-555-2035 1046 YES
1005 St. John Hospital 59652 Shelby Rd. Shelby Twp. MI 48317 586-569-6987 1050 NULL
1006 Salvation Army 56231 Somewhere Blvd. Eastpointe MI 48021 586-555-1212 1056 YES
1007 LA Angels Traders 2468 Halo Park Dr South Los Angelas MI 90234 903-965-3556 2015 NULL
1008 Purple Heart 28765 Van Dyke Sterling Heights MI 48313 586-732-8723 1061 NULL
1009 St. Raja Home 45875 West. Hill St. Utica MI 48045 586-795-3486 1062 NULL
1010 Mother Wattles 4568 Griswold Detroit MI 48205 313-478-9856 2016 YES
1011 Ron McDonald House 649 West Road Utica MI 48045 586-795-9979 1030 NULL
1012 St. Jude 262 Danny Thomas Place Memphis MI 38105 800-822-6344 1030 NULL
(13 rows affected)

Answer 1

From the docs:
When a DEFAULT definition is added to an existing column in a table, by default, the Database Engine applies the new default only to new rows of data that are added to the table. Existing data that was inserted by using the previous DEFAULT definition is unaffected. However, when you add a new column to an existing table, you can specify that the Database Engine insert the default value (specified by the DEFAULT definition) instead of a null value, into the new column for the existing rows in the table.
So when adding a DEFAULT definition to an existing column, you need to fill the existing rows yourself.

Answer 2

You cannot add a new default constraint to an existing column and update exiting NULL values in the same DDL operation. You'll need to explicitly update values NULL values to the desired value afterward.
You can, however, add a new column with a default constraint and apply the default value to all existing rows by specifying the WITH VALUES clause:
ALTER TABLE dbo.charity
ADD store char(10) NULL
CONSTRAINT df_charity_STORE DEFAULT 'No'
WITH VALUES;
This method allows you to add a new NOT NULL column too.
If you are running Enterprise (or Developer) edition of SQL Server, WITH VALUES is a meta-data only operation, which avoids updating every row in the table internally during the operation. The operation physically updates each row in the table in lessor editions.

Answer 3

There are two options here. You can update all null values like this;
update charity
set STORE = 'NO'
where STORE is null
or If you want to replace null values only when selecting them, you can use ISNULL statement.
select ISNULL(STORE,'NO') from charity
Also, adding constraint with default value for existing column doesn't update previous data. It sets default value for new coming rows.