CREATE DOMAIN UUID AS CHAR(16) CHARACTER SET OCTETS COLLATE OCTETS;
COMMIT WORK;

CREATE TABLE UUID_TEST
(
    UU_ID UUID NOT NULL,
    STR   VARCHAR(10) NOT NULL,
  CONSTRAINT UUID_TEST__PK PRIMARY KEY (UU_ID)
);
COMMIT WORK;


SET TERM ^;
CREATE OR ALTER TRIGGER UUID_TEST__TR_BI
  FOR UUID_TEST
  ACTIVE
  BEFORE INSERT OR UPDATE
  POSITION 0
AS
BEGIN
  IF (NEW.UU_ID IS NULL) THEN NEW.UU_ID = GEN_UUID();
END^
SET TERM ;^
COMMIT WORK;


INSERT INTO UUID_TEST (STR) VALUES ('One');
INSERT INTO UUID_TEST (STR) VALUES ('Two');
INSERT INTO UUID_TEST (STR) VALUES ('Three');
INSERT INTO UUID_TEST (STR) VALUES ('Four');
COMMIT WORK;

Query
------------------------------------------------
SELECT UUID_TO_CHAR(UU_ID), STR
  FROM UUID_TEST
  WHERE UU_ID = CHAR_TO_UUID('E7735FA5-33DA-47B3-BAD6-3CEF829C0748');

Plan
------------------------------------------------
PLAN (UUID_TEST INDEX (UUID_TEST__PK))

Query Time
------------------------------------------------
Prepare       : 31.00 ms
Execute       : 0.00 ms
Avg fetch time: 0.00 ms

Memory
------------------------------------------------
Current: 12 138 360
Max    : 13 923 248
Buffers: 2 048

Operations
------------------------------------------------
Read   : 0
Writes : 0
Fetches: 11
Marks  : 0


Enchanced Info:
+-------------------------------+-----------+-----------+-------------+---------+---------+---------+----------+----------+----------+
|          Table Name           |  Records  |  Indexed  | Non-Indexed | Updates | Deletes | Inserts | Backouts |  Purges  | Expunges |
|                               |   Total   |   reads   |    reads    |         |         |         |          |          |          |
+-------------------------------+-----------+-----------+-------------+---------+---------+---------+----------+----------+----------+
|UUID_TEST                      |         0 |         1 |           0 |       0 |       0 |       0 |        0 |        0 |        0 |
+-------------------------------+-----------+-----------+-------------+---------+---------+---------+----------+----------+----------+