SELECT count( DISTINCT homework_id ) finishHomeworkCount, count( 1 ) AS homeworkTitleCount, COALESCE ( ROUND(( sum( question_actual_result )/ NULLIF( count( 1 ), 0 )) * 100, 2 ), 0.00 ) AS homeworkCurrentRate, CASE WHEN homeworkCurrentRate = 100 THEN 'A' WHEN homeworkCurrentRate >= 80 AND homeworkCurrentRate < 100 THEN 'B' WHEN homeworkCurrentRate >= 60 AND homeworkCurrentRate < 80 THEN 'C' WHEN homeworkCurrentRate < 60 THEN 'D' END FROM zhzy_homework_homework_student_question zhhsq WHERE student_id = 490 AND question_actual_result IS NOT NULL AND homework_type = 1 AND update_time BETWEEN "2023-07-15" AND "2023-07-16" GROUP BY homework_id > 1054 - Unknown column 'homeworkCurrentRate' in 'field list' 如何修改

要解决这个问题，你需要做两个步骤：

1. 将 `homeworkCurrentRate` 移动到 `HAVING` 子句中，因为它是在 `SELECT` 子句中定义的别名。
2. 将 `CASE` 语句移动到外部查询中，以便你可以在 `SELECT` 子句中引用它。

下面是修改后的查询语句：

SELECT
    finishHomeworkCount,
    homeworkTitleCount,
    homeworkCurrentRate,
    CASE
        WHEN homeworkCurrentRate = 100 THEN 'A'
        WHEN homeworkCurrentRate >= 80 AND homeworkCurrentRate < 100 THEN 'B'
        WHEN homeworkCurrentRate >= 60 AND homeworkCurrentRate < 80 THEN 'C'
        WHEN homeworkCurrentRate < 60 THEN 'D'
    END AS grade
FROM (
    SELECT
        COUNT(DISTINCT homework_id) AS finishHomeworkCount,
        COUNT(1) AS homeworkTitleCount,
        COALESCE(ROUND((SUM(question_actual_result) / NULLIF(COUNT(1), 0)) * 100, 2), 0.00) AS homeworkCurrentRate
    FROM
        zhzy_homework_homework_student_question zhhsq
    WHERE
        student_id = 490
        AND question_actual_result IS NOT NULL
        AND homework_type = 1
        AND update_time BETWEEN "2023-07-15" AND "2023-07-16"
    GROUP BY
        homework_id
    HAVING
        homeworkCurrentRate IS NOT NULL
) AS subquery;

这样修改后的查询将会计算出每个作业的完成数量、作业标题数量以及作业的当前进度百分比，并根据百分比给出一个等级。