Question

--------------------------------
|uid |lesson_score |date       |
--------------------------------
|1   |2            |1391023460 |
|1   |4            |1391023518 |
|2   |3            |1391023557 |
|1   |8            |1391023596 |
--------------------------------

如何确定特定用户的最高和最低分数及其各自的日期？

到目前为止，我有这个：

SELECT MAX(lesson_score) AS max_lesson_score, MIN(lesson_score) AS min_lesson_score, date
FROM user_progress 
WHERE uid = 1

我需要得到的是：

min: 2, 1391023460
max: 8, 1391023460

我知道它正在返回正确的最低和最高分数，但它只返回一个日期，我甚至不确定它的返回日期......

谢谢！

Answer 1

您的查询不是合法的SQL，正是因为MIN和MAX得分有不同的数据值。

查询并不简单，因为您希望在不同的行中返回MIN和MAX。

SELECT lesson_score, date 
FROM user_progress
WHERE uid = 1
AND (
      lesson_score = (SELECT MAX(lesson_score) 
                      FROM user_progress
                      WHERE uid = 1)
   OR (lesson_score = (SELECT MIN(lesson_score)
                      FROM user_progress
                      WHERE uid = 1)
  )

如果你有多个lesson_score等于MIN或MAX，你会得到额外的行显示它。

Answer 2

快速修复：

SELECT MAX(lesson_score) AS max_lesson_score, MIN(lesson_score) AS min_lesson_score, date
FROM user_progress 
WHERE uid = 1
GROUP BY date

每当你有一个聚合函数（sum，count，max，min）时，你需要在GROUP BY中包含所有非聚合列，因此它知道在哪些列上执行这些函数。我希望这是有道理的。

SQL：获取最小值和最大值以及每个值的另一个相应列

2 个答案: