Question

我有一张这样的表：

CREATE TABLE `PQ_batch` (
  `id` int(6) unsigned NOT NULL AUTO_INCREMENT COMMENT 'Batch Id number',
  `date` datetime DEFAULT NULL,
  `qty` int(11) DEFAULT NULL COMMENT 'Number of units in a batch',
  PRIMARY KEY (`bid`)
) ENGINE=InnoDB AUTO_INCREMENT=1000 DEFAULT CHARSET=utf8;


Id    |    date       | qty
--------------------------------
1        2017-01-06     5
2        2017-01-02     5
3        2017-01-03     100

给定的数值： @qtyToTake：= 100

*选择满足@qtyToTake所需的行，并且仅选择这些行，从每行获取的数量以及该行剩余的新数量。最早的批次应该先用完。 *

看起来应该是这样的：

Id    |    date       | qty  |  newQty   | qtyTakenPerRecord
-------------------------------------------------------
1        2017-01-02     5       0           5 
2        2017-01-03     100     5           95 
3        2017-01-01     5       5           0

newQty =（qty - @qtyToTake）其中@qtyToTake =（@qtyToTake - 前一行＆＃39; s数量，直到@qtyToTake达到0）

@qtyToTake应动态分配为前一行的数量及其当前值的差值，直到达到0.

这是我想出的：

SELECT p.bid, p.Orig as origQty, p.NewQty, (p.Orig - p.NewQty) AS NumToTake 
        FROM( 
            SELECT  b.bid, (@runtot :=  b.bqty  - @runtot) AS remain, ( @runtot := (b.bqty - @runtot) ) leftToGet, b.bqty AS Orig,
             (SELECT
                 (sum(bqty) - @runtot) AS tot  FROM PQ_batch
               WHERE bid <= b.bid )  AS RunningTotal, 
               (SELECT
                  CASE  
                       WHEN (sum(bqty) - @runtot) > 1 THEN (sum(bqty) - @runtot)
                       ELSE 0
                   END
                    FROM PQ_batch
                    WHERE bid <= b.bid )   AS NewQty
            FROM    PQ_batch b,(SELECT @runtot:= 100) c
            ORDER BY bdate
         ) AS p

Answer 1

在这里使用@McNets示例＆＃39; s我想出的：

SELECT bid, bdate,bpid,bcost, bqty, newQty, qtyTakenPerRecord
        FROM (
                SELECT y.*,
                       IF(@qtyToTake > 0, 1, 0) AS used,
                       IF(@qtyToTake > bqty, 0, bqty - @qtyToTake) AS newQty,
                       IF(@qtyToTake > bqty, bqty, bqty - (bqty - @qtyToTake)) AS qtyTakenPerRecord,
                       @qtyToTake := @qtyToTake - bqty AS qtyToTake
                FROM
                    (SELECT @qtyToTake := 100) x,
                    (SELECT * from PQ_batch  WHERE bpid =1002 AND bqty > 0 ORDER BY bdate) y
             ) z
        WHERE used = 1
        ORDER BY bdate

MySQL滚动减去给定的数量

1 个答案: