计算 2 表 where 条件 - Linq

Question

我有 2 张桌子，

产品表

id  produk  batch   qty
1   AAA    ADADAD   2
2   BBB    ADADAD   2
3   BBB    AAAAAA   2
...............

然后移动桌子，

id  produk  batch   qty
1   BBB     ADADAD  1

我想在 stok 表中的 qty 减去 move 表中的 qty 之后显示表，我想要什么表

PRODUK  BATCH   QTY
AAA     ADADAD  2
BBB     ADADAD  1
BBB     AAAAAA  2

这是我的查询

var obj = _db.produk
       .Groupby(a=> new {a.code,a.batch})
       .Select(a=> new {
          produk = a.key.code,
          batch = a.Key.batch,
          qty = _db.move.Where(c => a.Any(p => p.code == a.code && p.batch == a.batch)).Sum(a=>a.qty)
       }).tolist();

但不工作

Answer 1

您必须对分组移动表执行 LEFT JOIN。

var moves =
  from m in _db.move
  group m by { m.code, m.batch } into g
  select
  {
      g.Key.code,
      g.Key.batch,
      qty = g.Sum(x => x.qty)
  };

var query = 
   from p in _db.produk
   join m in moves on new { p.code, p.batch } equals { m.code, m.batch } into j
   from m in j.DefaultIfEmpty()
   select new
   {
       produk = p.code,
       batch = p.batch.
       qty = p.qty - (int?)m.qty ?? 0
   };

Answer 2

如果您更喜欢方法语法而不是查询语法，那么您可以这样编写查询：

var availableItems = repository
    .GroupJoin(purchases,
        stock => new { stock.Product, stock.Batch }, 
        move => new { move.Product, move.Batch },
        (stock, moves) => new { Stock = stock, Moves = moves })
    .SelectMany(
        stockAndRelatedMoves => stockAndRelatedMoves.Moves.DefaultIfEmpty(), 
        (stockAndRelatedMoves, relatedMove) => new
        {
            stockAndRelatedMoves.Stock.Product,
            stockAndRelatedMoves.Stock.Batch,
            Quantity = stockAndRelatedMoves.Stock.Quantity - (relatedMove?.Quantity ?? 0)
        })
    .ToList();

如您所见，您需要使用GroupJoin 而不是Select，而不是简单的Select，您需要SelectMany 从连接的记录中检索项目。

一些解释：

• stock => new { stock.Product, stock.Batch }：这里使用匿名类型，因为在join中使用了多个字段
• stockAndRelatedMoves => stockAndRelatedMoves.Moves.DefaultIfEmpty(): 需要左外连接
• (relatedMove?.Quantity ?? 0): relatedMove 可以是 null 这就是为什么我们用 0 代替它

在上面的代码中，我使用了以下集合：

var repository = new List<Stock>
{
    new Stock { Id = 1, Product = "AAA", Batch = "ADADAD", Quantity = 2 },
    new Stock { Id = 2, Product = "BBB", Batch = "ADADAD", Quantity = 2 },
    new Stock { Id = 3, Product = "BBB", Batch = "AAAAAA", Quantity = 2 },
};

var purchases = new List<Move>
{
    new Move { Id = 1, Product = "BBB", Batch = "ADADAD", Quantity = 1 }
};

Answer 3

您也可以查询produck表，然后在Select语句中，根据产品的batch和produck属性过滤move表，然后计算qty。

代码如下：

        List<Produk> produks = new List<Produk>()
        {
            new Produk(){ id = 1, produk= "AAA", batch="ADADAD", qty = 2},
            new Produk(){ id = 2, produk= "BBB", batch="ADADAD", qty = 2},
            new Produk(){ id = 3, produk= "BBB", batch="AAAAAA", qty = 2},
        };

        List<Remove> removes = new List<Remove>()
        {
            new Remove(){ id=1, produk="BBB", batch="ADADAD", qty=1}
        };

        var result = (from p in produks
                      select new Produk
                      {
                          id = p.id,
                          produk = p.produk,
                          batch = p.batch,
                          qty = p.qty - removes.Where(c => c.produk == p.produk && c.batch == p.batch).Sum(c => c.qty)
                      }).ToList();

结果如下：