DB2 equivalent for MySQL's DROP .. IF EXISTS

No.

You'll need an IF clause to check for the existence of the table and then a separate statement to actually drop it if it does exist.

Alternative solution is given here:

Create the stored function db2perf_quiet_drop():

CREATE PROCEDURE db2perf_quiet_drop( IN statement VARCHAR(1000) )
LANGUAGE SQL
BEGIN
   DECLARE SQLSTATE CHAR(5);
   DECLARE NotThere    CONDITION FOR SQLSTATE '42704';
   DECLARE NotThereSig CONDITION FOR SQLSTATE '42883';

   DECLARE EXIT HANDLER FOR NotThere, NotThereSig
      SET SQLSTATE = '     ';

   SET statement = 'DROP ' || statement;
   EXECUTE IMMEDIATE statement;
END

and use it as Begin atomic call db2perf_quiet_drop('table my_table'); End

You can use an annonymous block

BEGIN
 DECLARE CONTINUE HANDLER FOR SQLSTATE '42704'
   BEGIN END;
 EXECUTE IMMEDIATE 'DROP TABLE sometable';
END @