sql min function and other column for sqlite - mysql

Question

For sqlite I see that such query return correct result:
CREATE TABLE users(id INTEGER PRIMARY KEY,
user_id INTEGER NOT NULL,
salary INTEGER NOT NULL);
insert into users (user_id, salary) values (1, 42000);
insert into users (user_id, salary) values (2, 39000);
insert into users (user_id, salary) values (3, 50000);
sqlite> SELECT user_id, MAX(salary) FROM users;
3|50000
sqlite> SELECT user_id, MIN(salary) FROM users;
2|39000
but looks like for mysql for example works in other way:
sql min function and other column
and return 1|50000.
Is it sqlite extension or may be mysql wrong in this case and this standard behaviour for SQL implementation?

Answer 1

The result is not "correct" in SQLite. SQLite extends its functionality to support these types of non-standard queries. This is clearly an extension of functionality, and one I wish it did not do.
The queries are non-standard because there is an unaggregated column in the SELECT (id) but the query is an aggregation query (because of the MIN()/MAX()). The more recent versions of MySQL with the default settings correctly reject this query as not syntactically correct. Older versions of MySQL return a value of id from an arbitrary row. SQLite has extended the definition of SQL for this special case and brings back the value of id that corresponds to the maximum or minimum salary.
In both databases, the better approach is:
SELECT user_id, salary as max_salary
FROM users
ORDER BY salary DESC
LIMIT 1;
and:
SELECT user_id, salary as min_salary
FROM users
ORDER BY salary ASC
LIMIT 1;