最低平均值

Question

我必须显示每年平均成绩最低的学生的姓名。 我使用的表具有以下结构：

students
s_name | s_id | year

grades
s_id | grade

我尝试的一切都无法正常工作。

SELECT s.s_name FROM students s JOIN grades g ON s.s_id=g.s_id
GROUP BY s.s_name, s.year HAVING AVG(g.grade) = (SELECT MIN(AVG(g.grade)) FROM students s JOIN grades g ON s.s_id=g.s_id GROUP BY s.year)

Answer 1

请尝试此查询：

    CREATE TABLE #STUDENT
    (
        S_NAME VARCHAR(2),
        S_ID INT IDENTITY(1,1) PRIMARY KEY,
        YEAR INT
    );
    CREATE TABLE #GRADES
    (
        S_ID INT IDENTITY(1,1) PRIMARY KEY,
        GRADE DECIMAL(3,2)
    );

    INSERT INTO #STUDENT VALUES('X1',2010);
    INSERT INTO #STUDENT VALUES('X2',2010);
    INSERT INTO #STUDENT VALUES('X3',2010);
    INSERT INTO #STUDENT VALUES('X4',2010);
    INSERT INTO #STUDENT VALUES('X5',2011);
    INSERT INTO #STUDENT VALUES('X6',2011);
    INSERT INTO #STUDENT VALUES('X7',2011);
    INSERT INTO #STUDENT VALUES('X8',2012);
    INSERT INTO #STUDENT VALUES('X8',2012);
    INSERT INTO #STUDENT VALUES('X8',2012);

    INSERT INTO #GRADES VALUES(6.5);
    INSERT INTO #GRADES VALUES(6.9);
    INSERT INTO #GRADES VALUES(7.3);
    INSERT INTO #GRADES VALUES(6.0);
    INSERT INTO #GRADES VALUES(7.9);
    INSERT INTO #GRADES VALUES(8.1);
    INSERT INTO #GRADES VALUES(6.6);
    INSERT INTO #GRADES VALUES(7.2);
    INSERT INTO #GRADES VALUES(7.6);
    INSERT INTO #GRADES VALUES(8.2);

    SELECT STUDENT_NAME, S_ID, YEAR, GRADE
    FROM (
        SELECT
            FIRST_VALUE(ST.S_NAME) OVER (PARTITION BY ST.YEAR ORDER BY GR.GRADE ASC) AS 'STUDENT_NAME', 
            ST.S_ID, ST.YEAR, GR.GRADE,
            ROW_NUMBER() OVER (PARTITION BY ST.YEAR ORDER BY GR.GRADE ASC) AS 'RANK'
        FROM #STUDENT ST
        INNER JOIN #GRADES GR ON ST.S_ID = GR.S_ID
    )A
    WHERE A.RANK = 1

    DROP TABLE #STUDENT
    DROP TABLE #GRADES