How do I view all records with data source as 1 if not 1 then use data source 2 but no duplicates

Question

I have a table that has the below columns

sk_item_id  item_code       item_desc                    sk_data_source
1           054486900       TRIM lh hotplate Whi                1
2           054486900       TRIM lh hotplate Whi                2
3           081423698       ARC3084 DG FRIT                     2
4           081744900       HANDBOOK<600G MK2>44PGX500          1

I want to display the records that are contained within data source 2 but if the record does not sit in data source 2 then display the record that is in data source 1 but I do not want any duplicates

so basically display all data from data source 2 if the item code is not in data source 2 then display the record

Answer 1

If using Postgresql, do DISTINCT ON:

select distinct on (item_code) sk_item_id, item_code, item_desc, sk_data_source 
from table_name
order by item_code, sk_data_source desc;