Question

I have a table Locations(id, type, code, parentid).

The type can be COUNTRY/STATE/REGION/TOWN. So this table holds hierarchical geographic data.
Country will have many states, state many regions and regions many towns.

I need to list out descendent records for a given parent record. For example I need all records under Country Australia. The parent record in this case will be

10, COUNTRY, AU, null)

I understand a recursive CTE is the way to go but not sure how to.

thanks

Answer 1

Here’s an example of a CTE approach:

declare @t table (id int, type varchar(10), name varchar(50), parentid int)
insert @t
          select 1, 'COUNTRY', 'AU', null
union all select 2, 'STATE', 'Guiness State', 1
union all select 3, 'STATE', 'Pilsner State', 1
union all select 4, 'REGION', 'Heineken Region', 2
union all select 5, 'REGION', 'Bud Light Region', 3
union all select 6, 'TOWN', 'Hoegaarden  Town', 2
union all select 7, 'TOWN', 'Corona Town', 2
union all select 8, 'TOWN', 'Leffe Town', 3

; with  recursed as
        (
        select  *
        from    @t as root
        where   root.name = 'Guiness State'
        union all
        select  child.*
        from    recursed as parent
        join    @t as child
        on      parent.id = child.parentid
        )
select  *
from    recursed

Code sample at SE Data.