SQL deletes columns with default values

Sometimes the online data structure changes. First back up the previous data and use a script to initialize it. However, when you delete a column with the default value, the script always reports an error. Google, so you can:

Use Mytestdb -- Delete constraints first
Declare   @ Name   Varchar ( 20 )
Select   @ Name   = B. Name From Sysobjects B Join Syscolumns On  
B. ID = A. cdefault Where A. ID =   Object_id ( ' Userinfo ' ) And A. Name =   ' Nickname '
Exec ( ' Alter table userinfo drop Constraint '   +   @ Name )

--Then you can delete the field.
Alter TableDBO. userinfoDrop ColumnNickname