Query below lists tables with most relationships (both foreign keys and FK references from other tables).

See also:

• Tables with most foreign keys
• Most referenced tables.

Query

select
    refFK.table,
    foreign_keys + coalesce(references,0) as relationships ,
    foreign_keys,
    coalesce(references,0) as references,
    referenced_tables + coalesce(referencing_tables,0) as related_tables,
    referenced_tables,
    coalesce(referencing_tables,0) as referencing_tables
from 
(   select 
    tabschema concat '.' concat tabname as table,
    count(constname) as foreign_keys,
    count(distinct reftabschema concat '.' concat reftabname)
                        as referenced_tables 
    from syscat.references
    group by tabschema concat '.' concat tabname
) refFK
left outer join
(   select 
    distinct reftabschema concat '.' concat reftabname as table,
    count(*) as references,
    count(distinct tabschema concat '.' concat tabname)
                    as referencing_tables 
    from syscat.references
    group by reftabschema concat '.' concat reftabname
) refbyFK on refFk.table = refbyFK.table
order by foreign_keys + COALESCE(references,0) desc

Columns

• table - name of table with schema name
• relationships - number of relationships (FKs and FK references)
• foreign_keys - number of foreign keys in a table
• references - number of FK references from other tables
• related_tables - number of different related tables (regardless of relationship type/direction table is counted only once)
• referenced_tables - nubmer of different tables referenced with FKs (please note that table can be related more than once so number of FKs and number of referenced tables can be different)
• referencing_tables - nubmer of different tables referencing with foreign keys this table

Rows

• One row represents one table in a database
• Scope of rows: all tables in a database
• Ordered by number of relationships (foreing keys and references) from the ones with the most

Sample results