Pegando a lista de tabelas em SQL com Firebird

 Para ver as tabelas no Firebird, use o seguinte SQL:

select rdb$relation_name
from rdb$relations
where rdb$view_blr is null
and (rdb$system_flag is null or rdb$system_flag = 0)
order by 1

Para ver a lista de campos de uma tabela, use o SQL:

select c.rdb$type_name, a.rdb$field_name, b.RDB$FIELD_SCALE
from rdb$relation_fields a, rdb$fields b, rdb$types c
where a.rdb$relation_name = 'MINHA_TABELA'
and a.RDB$FIELD_SOURCE = b.rdb$field_name
and b.rdb$field_type = c.rdb$type
and c.rdb$field_name = 'RDB$FIELD_TYPE'

Para ver os campos com chave primária:

select b.rdb$field_name
from RDB$relation_constraints a, RDB$INDEX_SEGMENTS b
where a.rdb$constraint_type = 'PRIMARY KEY'
and a.rdb$index_name = b.rdb$index_name
and a.rdb$relation_name = 'MINHA_TABELA'