Adding a uniqueidentifier column and adding the default to generate new guid

Question

I have the following SQL command:

ALTER TABLE dbo.UserProfiles
ADD ChatId UniqueIdentifier NOT NULL,
UNIQUE(ChatId),
CONSTRAINT \"ChatId_default\" SET DEFAUL         


        

Answer 1

Don't use newid() as default, instead use newsequentialid(). newid() creates a lot of fragmentation and that's bad for indexes.

As far as adding the new column to a table with existing data, simply do this:

    ALTER TABLE your_table
    ADD your_column UNIQUEIDENTIFIER DEFAULT newsequentialid() NOT null