Postgres 12

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CREATE TABLE tbl (
   user_id int
 , enabled bool
 , enabled_first bool DEFAULT true
  , PRIMARY KEY (user_id, enabled, enabled_first)
);

INSERT INTO tbl VALUES
  (123, false, true)
, (123, true, true)
, (123, true, false);

INSERT INTO tbl (user_id, enabled) VALUES
  (456, true);
3 rows affected

1 rows affected

TABLE tbl;


user_id
enabled
enabled_first


123
f
t

123
t
t

123
t
f

456
t
t


-- error
INSERT INTO tbl VALUES  (123, true, true);
ERROR:  duplicate key value violates unique constraint "tbl_pkey"
DETAIL:  Key (user_id, enabled, enabled_first)=(123, t, t) already exists.


-- allowed
INSERT INTO tbl VALUES  (123, false, false);
1 rows affected

TABLE tbl;


user_id
enabled
enabled_first


123
f
t

123
t
t

123
t
f

456
t
t

123
f
f