To be clearer, as you can name the primary key anything you want the statements from the article would miss any that do not begin with 'PK'.

declare @name_pk varchar(255)

select @name_pk = name from sysindexes where id in (select id from sysobjects where name = 'table_name') and name like 'PK%'

execute ('alter table table_name drop constraint ' + @name_pk)

So to get the name of the Primary Key Constraint without this restriction, using the same 'table_name' substitution:

declare @name_pk varchar(255)

SELECT @name_pk = constraint_name

FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS

WHERE constraint_type = 'PRIMARY KEY' and Table_name = 'table_name'

Print 'pk ' + @name_pk -- show the results

/* or use the execute as in the original */

-- execute ('alter table table_name drop constraint ' + @name_pk)

Toni