select

    rdb$relation_fields.rdb$relation_name table_name,

    rdb$relations.rdb$description table_des,

    rdb$relation_fields.rdb$field_name field_name,

    rdb$relation_fields.rdb$description field_des,

    rdb$types.rdb$type_name field_type,

    rdb$relation_fields.rdb$field_position seq,

    rdb$relation_fields.rdb$null_flag not_null,

    rdb$fields.RDB$FIELD_PRECISION precis,

    rdb$fields.rdb$field_scale scale

from rdb$types

   inner join rdb$fields on (rdb$types.rdb$type = rdb$fields.rdb$field_type)

   inner join rdb$relation_fields on (rdb$fields.rdb$field_name = rdb$relation_fields.rdb$field_source)

   inner join rdb$relations on (rdb$relation_fields.rdb$relation_name = rdb$relations.rdb$relation_name)

where rdb$relation_fields.rdb$system_flag =  and rdb$types.rdb$field_name = 'RDB$FIELD_TYPE'

order by rdb$relation_fields.rdb$relation_name, rdb$relation_fields.rdb$field_position