Change datatype of column to uniqueidentifier from bigint

Question

I want to change the datatype of a column in a table in sql server. I used the following statement:

ALTER TABLE dbo.tbltest  
ALTER COLUMN ID uniqueidentifie         


        

Answer 1

You cannot convert from an integer to a uniqueidentifier. But you can do it like this.

1. First delete old data from the table.

2. Alter the column to some text-format (such as VARCHAR(200)).

   ALTER TABLE dbo.tbltest  
   ALTER COLUMN ID VARCHAR(200)
   

3. Now again

   ALTER TABLE dbo.tbltest  
   ALTER COLUMN ID uniqueidentifier
   

To be clear, you can't convert a column from numeric to uniqueidentifier directly, but you can convert numeric to varchar to uniqueidentifier.