Question

Need some help with a query.. I have three tables.

Source
id      name
1       Other
2       Website
3       Wikipedia

Person
id      name
1       Tom
2       Lewis
3       Gary

person_source
person_sources_id  source_id
1                   2
1                   3
3                   3

I want to build a query that displays a person and a column for each source – displaying the name of the source if it exists in the relationship and a null if it doesnt:

output (for Tom)
-name-
null
Website
Wikipedia

I have the following query, but it gives me the sources attached to the contact, without the nulls..

    rs2 = s2.executeQuery("select distinct source.name "+
                        "from person left join person_source "+
                        "on person_source.person_sources_id = "+rs.getLong("id")+" join source "+
                        "on source.id = person_source.source_id");

My code’s current output for Tom:

Output (for Tom)
-name-
Website
Wikipedia

Thanks

Answer 1

if you already know the person id, you don’t need to join person table

select case when person_source.id is not null
            then source.name
       end "name"
from source
left join person_source
  on source.id = person_source.source_id
  and person_source.person_sources_id = :id
order by source.id