Obtener tipo de dato de campos con firebird

ASI

SELECT a.RDB$RELATION_NAME, b.RDB$FIELD_NAME, b.RDB$FIELD_ID, d.RDB$TYPE_NAME,
       c.RDB$FIELD_LENGTH, c.RDB$FIELD_SCALE
FROM   RDB$RELATIONS a
INNER JOIN RDB$RELATION_FIELDS b
ON     a.RDB$RELATION_NAME = b.RDB$RELATION_NAME
INNER JOIN RDB$FIELDS c
ON     b.RDB$FIELD_SOURCE = c.RDB$FIELD_NAME
INNER JOIN RDB$TYPES d
ON     c.RDB$FIELD_TYPE = d.RDB$TYPE
WHERE  a.RDB$SYSTEM_FLAG = 0
  AND  d.RDB$FIELD_NAME = 'RDB$FIELD_TYPE'
ORDER BY a.RDB$RELATION_NAME, b.RDB$FIELD_ID