MySQL 8.0

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select version();


version()


8.0.36


create table currency (id int, name text, primary key (id));
insert into currency (id, name) values (1, 'USD'), (2, 'EUR');

Records: 2  Duplicates: 0  Warnings: 0


create table selling (cur_id int, foreign key (cur_id) references currency(id));
insert into selling (cur_id) values (1);
create table buying (id_currency int, foreign key (id_currency) references currency(id));
insert into buying (id_currency) values (1);
select 
  group_concat(
    concat('select ''', table_schema, '.', table_name, ''' where exists (select null from ', table_schema, '.', table_name, ' where ', column_name, ' = @id)')
    separator '\nunion all\n'
  ) as query
from information_schema.key_column_usage
where upper(referenced_table_schema) = 'FIDDLE' -- your schema name here
  and upper(referenced_table_name) = 'CURRENCY';


query


select 'fiddle.selling' where exists (select null from fiddle.selling where cur_id = @id)
union all
select 'fiddle.buying' where exists (select null from fiddle.buying where id_currency = @id)


set @id = 1;
select 'fiddle.selling' where exists (select null from fiddle.selling where cur_id = @id)
union all
select 'fiddle.buying' where exists (select null from fiddle.buying where id_currency = @id)


fiddle.selling


fiddle.selling

fiddle.buying