This query listed tables that have no foreign keys, meaning they are not referencing any table or are not on the "many" side of FK.

Query below lists something a little different - tables that are not referencing and are not referenced by other tables. Something I called Loner Tables. This diagram illustrates the concept:

Learn more about Loner Tables

Query

select count(*) [table_count],
    sum(case when fks.cnt + refs.cnt = 0 then 1 else 0 end) 
    as [loner_tables],
    cast(cast(100.0 * sum(case when fks.cnt + refs.cnt = 0 then 1 else 0 end) 
    / count(*) as decimal(36, 1)) as varchar) + '%' as [loner_ratio]
from (select schema_name(tab.schema_id) + '.' + tab.name as tab,
        count(fk.name) cnt
    from sys.tables as tab
        left join sys.foreign_keys as fk
            on tab.object_id = fk.parent_object_id
    group by schema_name(tab.schema_id), tab.name) fks
    inner join 
    (select schema_name(tab.schema_id) + '.' + tab.name as tab,
        count(fk.name) cnt
    from sys.tables as tab
        left join sys.foreign_keys as fk
            on tab.object_id = fk.referenced_object_id
    group by schema_name(tab.schema_id), tab.name) refs
    on fks.tab = refs.tab

Columns

• table_count - number of tables in database
• loner_tables - number of Loner Tables in the database
• loner_ratio - Loner Ratio - % of Loner Tables in the database

Rows

• Scope of rows: query returns one row

Sample results

Loner Ratio in AdventureWorks sample database is 6.9%, meaning that 6.9% of tables are not related by foreign keys to any other table.