Express + Mongoose + 聚合 + 计算可用库存答案

【问题标题】：Express + Mongoose + Aggregation + Calculate Available StockExpress + Mongoose + 聚合 + 计算可用库存
【发布时间】：2021-08-05 09:31:48
【问题描述】：

我正在使用 express js 和 mongoose，我是这些平台的新手。如果有人可以帮助我，那就太好了。请参考以下数据，我正在寻找如下输出：

itemsizeId: 609578ca23033e55886e7590, AvailableQuantity: 112

itemsizeId: 609578ca23033e55886e758f, AvailableQuantity: 495

注意：按运动类型（向内/向外）分组。

可用库存：向内 - 向外

[
  {
    _id: '609fb1a1a7ed990f30d6cae2',
    refId: 'Purchase-1',
    itemsizeId: '609578ca23033e55886e7590',
    itemId: '609578ca23033e55886e758e',
    sizeId: '60950c0ba4982390f8dfed79',
    movementdate: '2021-05-15T11:33:52.894Z',
    movementtype: 'inward',
    movementcategory: 'purchase',
    quantity: 100,
    id: '609fb1a1a7ed990f30d6cae2',
  },
  {
    _id: '609fb1cba7ed990f30d6cae3',
    refId: 'Purchase-2',
    itemsizeId: '609578ca23033e55886e7590',
    itemId: '609578ca23033e55886e758e',
    sizeId: '60950c0ba4982390f8dfed79',
    movementdate: '2021-05-15T11:34:35.118Z',
    movementtype: 'inward',
    movementcategory: 'purchase',
    quantity: 20,
    id: '609fb1cba7ed990f30d6cae3',
  },
  {
    _id: '609fb1fda7ed990f30d6cae4',
    refId: 'Sale-1',
    itemsizeId: '609578ca23033e55886e7590',
    itemId: '609578ca23033e55886e758e',
    sizeId: '60950c0ba4982390f8dfed79',
    movementdate: '2021-05-15T11:35:25.068Z',
    movementtype: 'outward',
    movementcategory: 'sales',
    quantity: 5,
    id: '609fb1fda7ed990f30d6cae4',
  },
  {
    _id: '609fb255a7ed990f30d6cae5',
    refId: 'Purchase-3',
    itemsizeId: '609578ca23033e55886e758f',
    itemId: '609578ca23033e55886e758e',
    sizeId: '60950be9a4982390f8dfed78',
    movementdate: '2021-05-15T11:36:53.835Z',
    movementtype: 'inward',
    movementcategory: 'purchase',
    quantity: 500,
    id: '609fb255a7ed990f30d6cae5',
  },
  {
    _id: '609fb27ea7ed990f30d6cae6',
    refId: 'Sale-2',
    itemsizeId: '609578ca23033e55886e758f',
    itemId: '609578ca23033e55886e758e',
    sizeId: '60950be9a4982390f8dfed78',
    movementdate: '2021-05-15T11:37:34.066Z',
    movementtype: 'outward',
    movementcategory: 'sales',
    quantity: 8,
    id: '609fb27ea7ed990f30d6cae6',
  },
]

我已经尝试了下面的代码，我很高兴完成它：

const itemStock = await itemStockMovementModel.aggregate([
  {
    $match: { movementtype: 'inward' },
  },
  {
    $group: {
      _id: {
        itemsizeId: '$itemsizeId',
      },
      quantity: { $sum: '$quantity' },
    },
  },
])

【问题讨论】：

标签： mongodb express mongoose aggregation-framework stock

【解决方案1】：

$group by itemsizeId 并按条件获取 inward 和 outward 的数量总和
$subtract 到 inward - outward

const itemStock = await itemStockMovementModel.aggregate([
  {
    $group: {
      _id: "$itemsizeId",
      inward: {
        $sum: { $cond: [{ $eq: ["$movementtype", "inward"] }, "$quantity", 0] }
      },
      outward: {
        $sum: { $cond: [{ $eq: ["$movementtype", "outward"] }, "$quantity", 0] }
      }
    }
  },
  {
    $project: {
      quantity: {
        $subtract: ["$inward", "$outward"]
      }
    }
  }
])

Playground

如果您在movementtype 中没有第三个类型，您也可以使用第二个公式，

$groupitemsizeId
检查条件如果movementtype 是inward 然后求和quantity 否则求和为负quantity

const itemStock = await itemStockMovementModel.aggregate([
  {
    $group: {
      _id: "$itemsizeId",
      quantity: {
        $sum: {
          $cond: [
            { $eq: ["$movementtype", "inward"] },
            "$quantity",
            { $subtract: [0, "$quantity"] }
          ]
        }
      }
    }
  }
])

Playground

【讨论】：