SQL 一对多关系表的统计 的更优解是什么?

比如问题是: 成绩达到过 80 以上的同学有几位?

示例表:

table test_students
name | studentID
Jim  | 1001

table test_scoresheet
studentID | date       | score
1001      | 2019-09-24 | 81
1001      | 2019-10-24 | 85

以 PostgreSQL 为例:

创建测试表及数据:

CREATE TABLE "public"."test_students" ("studentID" serial,"name" text, PRIMARY KEY ("studentID"));
INSERT INTO "public"."test_students" ("studentID", "name") VALUES ('1001', 'Jim');

CREATE TABLE "public"."test_scoresheet" ("id" serial,"studentID" int4, "date" text, "score" int4, PRIMARY KEY ("id"));
INSERT INTO "public"."test_scoresheet" ("id", "studentID", "date", "score") VALUES ('1', '1001', '2019-09-24', '81');
INSERT INTO "public"."test_scoresheet" ("id", "studentID", "date", "score") VALUES ('2', '1001', '2019-10-24', '85');

已知但预计不够良好的解法:

SELECT COUNT(id) FROM (
	SELECT
		DISTINCT ON(test_students."studentID")
		test_students."studentID" AS id
	FROM test_students
		INNER JOIN test_scoresheet ON test_students."studentID" = test_scoresheet."studentID"
) AS some_students;