Postgres 14

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create table t1 (id	int,subject	varchar(20), day varchar(20), event varchar(20));
insert into t1 values(211,	'maths'	,'mon',	'asmnt');
insert into t1 values(222,	'maths'	,'tue',	'asmnt');
insert into t1 values(223,	'science'	,'mon',	'test');
insert into t1 values(224,	'science'	,'tue',	'asmt');
insert into t1 values(225,	'science'	,'wed',	'insp');
insert into t1 values(226,	'computers'	,'mon',	'asmt');
insert into t1 values(227,	'maths'	,'mon',	'test');
insert into t1 values(228,	'computers'	,'mon',	'insp');
insert into t1 values(229,	'computers'	,'thr',	'asmnt');
insert into t1 values(230,	'computers'	,'fri',	'asmnt');
1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

SELECT * FROM t1 a
WHERE subject not in
                (
                  SELECT subject FROM t1 b WHERE b.event='test'
                )
order by id
Limit 1


id
subject
day
event


226
computers
mon
asmt


SELECT * FROM t1 a
WHERE not exists 
                (
                  SELECT 1 FROM t1 b WHERE b.event='test' and a.subject=b.subject
                )
order by id
Limit 1


id
subject
day
event


226
computers
mon
asmt