Postgres 14

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CREATE TABLE tbl (id int, val boolean);
INSERT INTO tbl VALUES
  (1, true)
, (2, false)
, (3, null)
;

CREATE TABLE

INSERT 0 3

SELECT * FROM tbl WHERE val;
SELECT * FROM tbl WHERE NOT val;
SELECT * FROM tbl WHERE val IS NULL;

id
val

1
t

SELECT 1

id
val

2
f

SELECT 1

id
val

3
null

SELECT 1

SELECT * FROM tbl WHERE val IS NOT TRUE;
SELECT * FROM tbl WHERE val IS NOT FALSE;
SELECT * FROM tbl WHERE val IS NOT NULL;

id
val

2
f

3
null

SELECT 2

id
val

1
t

3
null

SELECT 2

id
val

1
t

2
f

SELECT 2

id	val
2	f
3	null

id	val
1	t
3	null