[sql] Count distinct value pairs in multiple columns in SQL

What query will count the number of rows, but distinct by three parameters?

Example:

Id      Name        Address 
==============================
1     MyName        MyAddress
2     MySecondName  Address2

Something like:

select count(distinct id,name,address) from mytable

You can also do something like:

SELECT COUNT(DISTINCT id + name + address) FROM mytable

Get all distinct id, name and address columns and count the resulting rows.

SELECT COUNT(*) FROM mytable GROUP BY id, name, address

Having to return the count of a unique Bill of Materials (BOM) where each BOM have multiple positions, I dd something like this:

select t_item, t_pono, count(distinct ltrim(rtrim(t_item)) + cast(t_pono as varchar(3))) as [BOM Pono Count]
from BOMMaster
where t_pono = 1
group by t_item, t_pono

Given t_pono is a smallint datatype and t_item is a varchar(16) datatype

Another (probably not production-ready or recommended) method I just came up with is to concat the values to a string and count this string distinctively:

SELECT count(DISTINCT concat(id, name, address)) FROM mytable;