Postgres 14 delete with count in where clause - postgresql

Question

I wanted to delete all records except the one with the highest value so I did
CREATE TABLE code (
id SERIAL,
name VARCHAR(255) NOT NULL ,
value int NOT NULL
);
INSERT INTO code (name,value) VALUES ('name',1);
INSERT INTO code (name,value) VALUES ('name',2);
INSERT INTO code (name,value) VALUES ('name',3);
INSERT INTO code (name,value) VALUES ('name1',3);
INSERT INTO code (name,value) VALUES ('name2',1);
INSERT INTO code (name,value) VALUES ('name2',3);
Example I want to delete all records except the one with the highest value on value column
I am expecting to get result as:
name 3
name1 3
name2 3
I tried doing
DELETE FROM code where value != (select MAX(value) value from code where count(code) > 1)
But I'm getting an error like:
ERROR: aggregate functions are not allowed in WHERE
LINE 1: ...value != (select MAX(value) value from code where count(code...
With everyone's idea and combine with this
SELECT dept, SUM(expense) FROM records
WHERE ROW(year, dept) IN (SELECT x, y FROM otherTable)
GROUP BY dept;
link
I was able to make the query I want
Demo

Answer 1

Your query makes no sense. Try this:
DELETE FROM code
where value <> (select value
FROM (SELECT count(*) AS count,
value
from code
GROUP BY value) AS q
ORDER BY count DESC
FETCH FIRST 1 ROWS ONLY);

Answer 2

The fast and easy solution would be:
BEGIN;
SELECT name,max(value) INTO temp t FROM code group by 1;
TRUNCATE code;
insert into code SELECT * FROM t;
END;
Or you can do like:
BEGIN;
DELETE FROM code USING (SELECT name,max(value) FROM code group by 1) a WHERE code.name=a.name AND code.value!=a.max;
END;