查询中的累计和

Question

对于大于或小于指定值的行，如何返回累积和的行？

表：

id | count
-----------
1 | 30
2 | 10
3 | 5
4 | 20
5 | 15

查询：

SELECT id, count
FROM table
ORDER BY id
HAVING SUM(count) < 50

返回行：

id | count
-------------
1 | 30
2 | 10
3 | 5

更新

代码：

public function query(){
    switch($this->table){
        case 'in_stock':
            return "SELECT * FROM ".Init::$static['db'].".stock
                WHERE id<=dynaccount.stock_first_available_id(".$this->value['num_stock'].", ".$this->value['product_id'].", ".(isset($this->att_arr['gid']) ? $this->att_arr['gid']:$_SESSION['gid']).")
                ORDER BY time, id";
    }
}

程序：

DELIMITER $$

DROP FUNCTION IF EXISTS `stock_first_available_id` $$
CREATE DEFINER=`dynaccount`@`localhost` FUNCTION `stock_first_available_id`(_running_total_limit INT, _product_id INT, _group_id INT) RETURNS INT
BEGIN
    DECLARE _running_count INT default 0;
    DECLARE _id INT;
    DECLARE _current_id INT;
    DECLARE _sum_count INT;

    IF (SELECT COUNT(*) FROM stock WHERE group_id=_group_id && type=2 && product_id=_product_id) = 0 THEN
        RETURN 0;
    END IF;

    DECLARE _cur CURSOR FOR SELECT id, count FROM stock WHERE group_id=_group_id && type=2 && product_id=_product_id ORDER BY time DESC, id DESC;

    OPEN _cur;

    read_loop: LOOP
        FETCH _cur INTO _id, _sum_count;

        SET _running_count = _running_count + _sum_count;
        SET _current_id = _id;

        IF _running_count > _running_total_limit THEN
            LEAVE read_loop;
        END IF;
    END LOOP read_loop;

    CLOSE _cur;

    RETURN _current_id;
END $$

DELIMITER ;

错误：

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DECLARE _cur CURSOR FOR SELECT id, count FROM stock WHERE group_id=_group_id && ' at line 12 

Answer 1

以下查询：

SELECT * FROM 
(SELECT id, 
       count, 
       @running_count := @running_count + count AS Counter 
  FROM sumtest, (SELECT @running_count := 0) AS T1 ORDER BY id) AS TableCount 

WHERE TableCount.Counter < 50;

产生结果：

id  count   Counter
1   30      30
2   10      40
3   5       45

我将您的表复制到 MySql 中，并将其称为“sumtest”顺便说一句。请替换为您的表名。

实际上，我们按照 id 顺序计算出运行总数，然后将其用作子查询。

所以这个查询：

SELECT id, 
       count, 
       @running_count := @running_count + count AS Counter 
FROM sumtest, (SELECT @running_count := 0) AS T1 
ORDER BY id

生产：

id  count   Counter
1   30      30
2   10      40
3   5       45
4   20      65
5   15      80

因此，通过对其执行另一次选择来选择计数器小于所需总和的所有行就变得微不足道了。

编辑：这是一个带有光标的示例。我刚刚为你整理了这个函数（注意我的表叫做 sumtest，我的帐户是默认的 root@localhost）：

DELIMITER $$

DROP FUNCTION IF EXISTS `Test_Cursing` $$
CREATE DEFINER=`root`@`localhost` FUNCTION `Test_Cursing`(_running_total_limit INT) RETURNS int
BEGIN
  /* Why am I on StackOverflow at 01:41 on New Years Day. Dear oh dear, where's the beer? */
  DECLARE _running_count INT default 0;
  DECLARE _id INT;
  DECLARE _current_id INT;
  DECLARE _sum_count INT;

  DECLARE _cur CURSOR FOR SELECT id, count FROM sumtest ORDER BY id;

  OPEN _cur;

  read_loop: LOOP
    FETCH _cur INTO _id, _sum_count;

    SET _running_count = _running_count + _sum_count;

    IF _running_count > _running_total_limit   THEN
      LEAVE read_loop;
    END IF;

    SET _current_id = _id;

  END LOOP;

  CLOSE _cur;

    RETURN _current_id;

END $$

DELIMITER ;

这样称呼它：

SELECT Test_Cursing(50);

将返回 id = 3 - 即超出运行总数限制之前的最后一个 id。然后您可以使用它来：

 SELECT * FROM sumtest WHERE id <= Test_Cursing(50);

返回：

id  count
1   30
2   10
3   5