Question

我在PostgreSQL中有一个查询，产生：

itemorder   name    qty
  1          A       -20
  2          A2       350
  3          A        50
  4          A        -10
  5          A2       10

itemorder列提供了我希望看到的正确的行顺序。我需要从下到上传递行，并为100的每一行计算一个初始值为+ qty且A为itemorder name qty modifyed_sum 1 A -20 120 / 140 + (-20) 2 A2 350 140 / not A 3 A 50 140 / 90 + 50 4 A -10 90 / 100 + (-10) 5 A2 10 100 / not A的新列。

public static boolean isPaladrome(int mNumber) {
    String numToString = String.valueOf(mNumber);
    int sLength = numToString.length();
    int midPoint = sLength / 2;
    return (new StringBuilder(numToString.substring(0, midPoint)).reverse()
            .toString()).equals(numToString.substring(sLength - midPoint));
}

我该怎么做？

Answer 1

试试这个

SELECT 100+ Sum(CASE WHEN name = 'a' THEN qty ELSE 0 END)OVER(ORDER BY itemorder DESC) as modifyed_sum,
       qty,
       name,
       itemorder
FROM   Yourtable
ORDER  BY itemorder ASC

另一种方式

SELECT 100 + (SELECT Sum(CASE WHEN b.name = 'a' THEN b.qty ELSE 0 END)
              FROM   yourtable  b
              WHERE  a.itemorder <= b.itemorder),
       qty,
       name,
       itemorder
FROM   yourtable a
ORDER  BY itemorder ASC

Answer 2

SELECT itemorder
     , name
     , qty
     , 100 + SUM(CASE WHEN name = 'A' THEN qty ELSE 0 END)
             OVER (ORDER BY itemorder ASC ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) AS modifyed_sum
    FROM thetable
    ORDER BY itemorder;

ROWS BETWEEN …功能a value expression将在window function中使用。

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