CREATE OR ALTER trigger table_1_bi0 for table_1
active before insert position 0
as

declare variable T_ID_1 integer;
declare variable T_ID_2 integer;
declare variable T_STR_1 varchar(255);
declare variable T_STR_2 varchar(255);
declare variable T_STR_3 varchar(255);
declare variable T_STR_5 varchar(255);
declare variable T_STR_6 varchar(255);
declare variable T_STR_7 varchar(255);

begin
  select position(',' in new.FIELD1) - 1
  from RDB$DATABASE
  into :T_ID_1;
  select substring(new.FIELD1 from 1 for :T_ID_1)
  from RDB$DATABASE
  into :T_STR_1;

  select trim(leading :T_STR_1 from new.FIELD1)
  from RDB$DATABASE
  into :T_STR_2;

  select trim(leading ',' from :T_STR_2)
  from RDB$DATABASE
  into :T_STR_5;

  new.FIELD2 = :T_STR_1;

  select position(',' in :T_STR_5) - 1
  from RDB$DATABASE
  into :T_ID_2;

  select substring(:T_STR_5 from 1 for :T_ID_2)
  from RDB$DATABASE
  into :T_STR_3;

  select trim(leading :T_STR_3 from :T_STR_5)
  from RDB$DATABASE
  into :T_STR_6;

  select trim(leading ',' from :T_STR_6)
  from RDB$DATABASE
  into :T_STR_7;

  new.FIELD3 = :T_STR_3;

  new.FIELD4 = :T_STR_7;

end