select
    rf.rdb$relation_name tab_name
    ,rf.rdb$field_position fld_pos
    ,rf.rdb$field_name fld_name
    ,case f.rdb$field_type
        when 7 then 'smallint'
        when 8 then 'integer'
        when 10 then 'float'
        when 14 then 'char(' || cast(cast(f.rdb$field_length / cx.div as int) as varchar(5)) || ')'
        when 16 then -- dialect 3 only
          case f.rdb$field_sub_type
            when 0 then 'bigint'
            when 1 then 'numeric(15,' || cast(-f.rdb$field_scale as varchar(6)) || ')'
            when 2 then 'decimal(15,' || cast(-f.rdb$field_scale as varchar(6)) || ')'
            else 'unknown'
          end
        when 12 then 'date'
        when 13 then 'time'
        when 27 then -- dialect 1 only
          case f.rdb$field_scale
            when 0 then 'double precision'
            else 'numeric(15,' || cast(-f.rdb$field_scale as varchar(6)) || ')'
          end
        when 35 then iif(di=1, 'date', 'timestamp')
        when 37 then 'varchar(' || cast(cast(f.rdb$field_length / cx.div as int) as varchar(5)) || ')'
        when 261 then 'blob sub_type ' || f.rdb$field_sub_type || ' segment size ' || f.rdb$segment_length
        else 'unknown'
    end fld_type
    ,cx.fld_charset
    ,cx.fld_collation
from (select m.mon$sql_dialect di from mon$database m) m
join rdb$relation_fields rf on 1=1
join rdb$relations rr on rf.rdb$relation_name=rr.rdb$relation_name
join rdb$fields f on rf.rdb$field_source=f.rdb$field_name
left join (
    select
        co.rdb$character_set_id fld_cset_id,
        co.rdb$collation_id fld_coll_id,
        co.rdb$collation_name fld_collation,
        rdb$character_set_name fld_charset,
        decode( ce.rdb$character_set_name,  upper('utf8'), 4, upper('unicode_fss'), 3,  1) div
    from rdb$collations co
    join rdb$character_sets ce on co.rdb$character_set_id=ce.rdb$character_set_id
) cx on  f.rdb$character_set_id=cx.fld_cset_id and f.rdb$collation_id = cx.fld_coll_id
where
    coalesce(rf.rdb$system_flag,0)=0
    and coalesce(rr.rdb$system_flag,0)=0
    and rr.rdb$relation_type in (0,4,5)
;