>>Why don't you use DEFAULT constraint and avoid UPDATE that in this case requires table lock?
>>

>>SET @ExecuteSql = N'ALTER TABLE [Client] ADD [test4] char(40) DEFAULT ('''')'
>>

>>
>>Also, wouldn't varchar(40) better choice for the column?
>
>I wasn't aware of the Default clause. Thanks for mentioning it.
>
>I have been used to Char(). Is VarChar() a new standard? Basically, if I define a character field, is this a better type to use?

Yes, for big character fields you may want to use Varchar fields as they take less space assuming you don't need your data to be 40 characters always.

There is a great article http://aboutsqlserver.com/2010/08/11/how-sql-server-stores-data-extents-data-pages-data-row-for-in-row-data/ explaining the innards of SQL Server.