Question

在这里学习SQL，我遇到了挑战。

我有下表：

tbl <- data.frame(
   id_name = c("a", "a", "b", "c", "d", "f", "b", "c", "d", "f"),
   value = c(1, -1, 1, 1, 1, 1, -1, -1, -1, -1),
   score = c(1, 0, 1, 2, 3, 4, 3, 2, 1, 0),
   date = as.Date(c("2001-1-1", "2002-1-1", "2003-1-1", "2005-1-1", 
                    "2005-1-1", "2007-1-1", "2008-1-1", "2010-1-1", 
                    "2011-1-1", "2012-1-1"), "%Y-%m-%d")
                   )


+---------+-------+-------+-----------+
| id_name | value | score |   date    |
+---------+-------+-------+-----------+
| a       |     1 |     1 |  2001-1-1 |
|  a      |    -1 |     0 |  2002-1-1 |
|  b      |     1 |     1 |  2003-1-1 |
|  c      |     1 |     2 |  2005-1-1 |
|  d      |     1 |     3 |  2005-1-1 |
|  f      |     1 |     4 |  2007-1-1 |
|  b      |    -1 |     3 |  2008-1-1 |
|  c      |    -1 |     2 |  2010-1-1 |
|  d      |    -1 |     1 |  2011-1-1 |
|  f      |    -1 |     0 |  2012-1-1 |
+---------+-------+-------+-----------+

我的目标是：

对于每个id_name，我想在当前行= id_name（包括）的日期之间获得tbl的最高分数（如果是破坏者）

例如，id_name＆＃39; a＆＃39;应该返回＆＃39; 2001-1-1＆＃39;因为它的分数是1 id_name＆＃39; b＆＃39;应该返回＆＃39; 2007-1-1＆＃39;因为它的分数是4：

+---------+----------+
| id_name |   date   |
+---------+----------+
| a       | 2001-1-1 |
| b       | 2007-1-1 |
+---------+----------+

这是我到目前为止所做的，

   sqldf("
  SELECT 
    id_name,
    date,
    score
  FROM
    tbl As d
  WHERE
    score = (
                        SELECT MAX(score)
                        FROM tbl As b
                        WHERE 
                          date >= (
                                        SELECT MIN(date)
                                        FROM tbl
                                        WHERE id_name = b.id_name
                          ) AND
                          date <= (
                                        SELECT MAX(date)
                                        FROM tbl
                                        WHERE id_name = b.id_name
                          )
    )
  ")

问题是它返回具有全局最大值的行，而与当前行值无关

谢谢！

Answer 1

我认为WHERE子句中的相关子查询符合这个要求：

SELECT id_name, date
FROM tbl as t1
WHERE score = (SELECT max(score) FROM tbl WHERE id_name = t1.id_name)

两个日期之间的每一行获得最大值？

1 个答案: