Generate guid for a table without a loop

Question

I have a table with 100 records with no PK.

I need to add random GUID to it. Before:

    First Name   Last Name   GUID
      John         Smith
      Alex         Smith
etc

After:

    First Name   Last Name   GUID
      John         Smith    34234234gyerfw
      Alex         Smith    werwer32r23r
etc

Currently I can do it by:

Creating an identity column with values, then make a while loop and generate newid(). Any option on how to do this without a loop?

Answer 1

Just add the empty column and then do an UPDATE .

ALTER TABLE YourTable
ADD GUID UNIQUEIDENTIFIER

UPDATE YourTable
SET GUID = NEWID()

Answer 2

Add the GUID column as NOT NULL with a default of NEWID()

ALTER TABLE
    [dbo].[Text]

ADD [GUID] uniqueidentifier NOT NULL DEFAULT NEWID()

This will automatically populate the existing rows, an you will not need to specify a guid when inserting records.

Answer 3

You can add a column and update the value or create a persisted column that has a default constraint with NEWID()

create table test (id int identity
, column1 uniqueidentifier not null default newid()
, column2 varchar(10))

insert into test(column2)
values ('a')

select * from test

alter table test
add column3 uniqueidentifier

update test
set column3 = NEWID()