Question

您可以将以下查询翻译成linq吗？ ... 我正在使用实体框架核心并尝试使用存储过程，但似乎我必须创建一个适用于存储过程的元数据的模型。所以我试图了解这种查询是否可以转换为linq，因此我不必创建单独的数据库模型。

    SELECT 
    Stock.stockID ProductID, 
    stockName ProductName, 
    categoryName ProductCategory, 
    typeName ProductType, 
    sizeName ProductSize, 
    currentQuantity CurrentQuantity, 
    standardQuantity QuantityPerBox, 
    CONVERT(VARCHAR(255),CONVERT(INT,Stock.price)) AvgUnitCost,
    CONVERT(VARCHAR(255),CONVERT(INT,x.lastUnitCost)) LastOrderUnitCost,
    CONVERT(VARCHAR(10),CONVERT(DATE,x.lastOrderDate)) LastOrderDate
FROM dbo.Stock
LEFT JOIN 
(
SELECT stockID,unitPrice lastUnitCost ,orderDate lastOrderDate, ROW_NUMBER() OVER (PARTITION BY stockID ORDER BY orderDate DESC) rn FROM dbo.SalesOrder 
    JOIN dbo.SalesOrderDetail ON SalesOrderDetail.salesOrderID = SalesOrder.salesOrderID
WHERE customerID = @customerID AND salesStatus = 'S'
) x ON x.stockID = Stock.stockID AND rn = 1
LEFT JOIN dbo.StockCategory ON StockCategory.stockCategoryID = Stock.stockCategoryID
LEFT JOIN dbo.StockType ON StockType.stockTypeID = Stock.stockTypeID
LEFT JOIN dbo.StockSize ON StockSize.stockSizeID = Stock.stockSizeID
WHERE disStock = 0

Answer 1

几乎一切皆有可能。你只需要小心表现。

var query = 
    from stock in db.Stocks
    join x in (
      from grp in (
        from so in db.SalesOrders
        join sod in db.SalesOrderDetails on so.SalesOrderId equals sod.SalesOrderId
        where so.CustomerId == customerId && so.SalesStatus == "S"
        orderby so.OrderDate descending
        select new {
            sod.StockId, 
            LastUnitCost = sod.UnitPrice,
            LastOrderDate = so.OrderDate
        } into inner
        group inner by inner.StockId)
      select grp.Take(1)) on x.StockId equals stock.StockId into lastStockSales
    from x in lastStockSales.DefaultIfEmpty()
    join sc in db.StockCategories on stock.StockCatergotyId equals sc.StockCategoryId into scLeft
    from sc in scLeft.DefaultIfEmpty()
    join st in db.StockTypes on stock.StockTypeId equals st.StockTypeId into stLeft
    from st in stLeft.DefaultIfEmpty()
    join ss in db.StockSizes on stock.StockSizeId equals ss.StockSizeId into ssLeft
    from ss in ssLeft.DefaultIfEmpty()
    where stock.DisStock == 0
    select new MyDTO {
      ProductId = stock.StockId,
      ProductName = stock.StockName,
      ProductType = st.TypeName,
      ProductSize = ss.SizeName,
      CurrentQuantity = stock.CurrentQuantity,
      QuantityPerBox = stock.StandardQuantity,
      AvgUnitCost = stock.Price,
      LastOrderUnitCost = x.LastUnitCost,
      LastOrderDate = x.LastOrderDate
    };

正如您所看到的，很容易重写这些查询，我不得不改变一些关于如何获得库存项目的最新销售的逻辑，因为从LINQ角度来看不支持ROW_NUMBER() OVER (PARTITION...。同样，在重写查询时，您必须考虑性能。

希望这有帮助。

linq子查询加入和分组

1 个答案: