SET BIND

-- native
SELECT CAST('123.45' AS DECFLOAT(16)) FROM RDB$DATABASE;

                   CAST
=======================
                 123.45

-- double
SET BIND OF DECFLOAT TO DOUBLE PRECISION;
SELECT CAST('123.45' AS DECFLOAT(16)) FROM RDB$DATABASE;

                   CAST
=======================
      123.4500000000000

-- still double
SET BIND OF DECFLOAT(34) TO CHAR;
SELECT CAST('123.45' AS DECFLOAT(16)) FROM RDB$DATABASE;

                   CAST
=======================
      123.4500000000000

-- text
SELECT CAST('123.45' AS DECFLOAT(34)) FROM RDB$DATABASE;

CAST
==========================================
123.45

SELECT CURRENT_TIMESTAMP FROM RDB$DATABASE;

                                        CURRENT_TIMESTAMP
=========================================================
2020-02-21 16:26:48.0230 GMT*

SET BIND OF TIME ZONE TO EXTENDED;
SELECT CURRENT_TIMESTAMP FROM RDB$DATABASE;

                                        CURRENT_TIMESTAMP
=========================================================
2020-02-21 19:26:55.6820 +03:00

SET DECFLOAT
  { ROUND <round_mode>
  | TRAPS TO [<trap_opt> [, <trap_opt> ...]] }

<round_mode> ::=
    CEILING | UP | HALF_UP | HALF_EVEN
  | HALF_DOWN | DOWN | FLOOR | REROUND

<trap_opt> ::=
    DIVISON_BY_ZERO | INEXACT | INVALID_OPERATION
  | OVERFLOW | UNDERFLOW