AppBoxFuture: Sql存儲的ORM查詢示例

  上篇介紹集成第三方Sql數據庫時未實現如導航屬性、子查詢等功能，經過大半個月的努力作者初步實現了這些功能，基本上能滿足80%-90%查詢需求，特別復雜的查詢可以用原生sql來處理，下面分別示例介紹。

Like/In/NotIn

public async Task<object> Query()
{
    var codes = new string[] { "001", "003" };
    var q = new SqlQuery<Entities.OrderItem>();
    q.Where(t => t.ProductCode.In(codes));
    q.AndWhere(t => t.Product.Name.Contains("Pro"));
    return await q.ToListAsync();
}

Select t."OrderId",t."ProductCode",t."Quantity" From "OrderItem" t Left Join "Product" j1 On j1."Code"=t."ProductCode" Where t."ProductCode" In (@p1,@p2) And j1."Name" Like @p3

分頁查詢

public async Task<object> Query()
{
    var q = new SqlQuery<Entities.OrderItem>();
    q.Where(t => t.Quantity > 0);
    q.OrderBy(t => t.ProductCode);
    q.Skip(2).Take(2);
    var totalRows = await q.CountAsync();
    return await q.ToListAsync();
}

Select Count(*) From "OrderItem" t Where t."Quantity" > @p1

Select t."OrderId",t."ProductCode",t."Quantity" From "OrderItem" t Where t."Quantity" > @p1 Order By t."ProductCode" Offset 2 Limit 2

EntityRef屬性自動Left Join

  適用於實體建模時指定了EntityRef(一對一關系)。

public async Task<object> Query()
{
    var q = new SqlQuery<Entities.Customer>();
    q.Where(t => t.City.Name == "無錫");
    return await q.ToListAsync(t => new { t.Id, t.Name, CityName = t.City.Name });
}

Select t."Id",t."Name",j1."Name" "CityName" From "Customer" t Left Join "City" j1 On j1."Code"=t."CityCode" Where j1."Name" = @p1

手工Join

  適用於實體建模時未指定EntityRef關系。

public async Task<object> Query()
{
    var q = new SqlQuery<Entities.Customer>();
    var j = new SqlQueryJoin<Entities.City>();

    q.LeftJoin(j, (cus, city) => cus.CityCode == city.Code);
    q.Where(j, (cus, city) => city.Name == "無錫");
    return await q.ToListAsync(j, (cus, city) => new { cus.Id, cus.Name, CityName = city.Name });
}

Select t."Id",t."Name",j1."Name" "CityName" From "Customer" t Left Join "City" j1 On j1."Code"=t."CityCode" Where j1."Name" = @p1

GroupBy分組

public async Task<object> Query()
{
    var q = new SqlQuery<Entities.OrderItem>();
    q.GroupBy(t => t.ProductCode)
        .Having(t => DbFuncs.Sum(t.Quantity) > 0);
    return await q.ToListAsync(t => new { t.ProductCode, Amount = DbFuncs.Sum(t.Quantity) });
}

Select t."ProductCode",Sum(t."Quantity") "Amount" From "OrderItem" t Group By t."ProductCode" Having Sum(t."Quantity") > @p1

SubQuery子查詢

public async Task<object> Query()
{
    var q = new SqlQuery<Entities.OrderItem>();
    var s = new SqlQuery<Entities.Product>();

    q.Where(t => t.ProductCode.In(
        s.Where(p => p.Name.Contains("15")).AsSubQuery(p => p.Code)
        ));
    return await q.ToListAsync();
}

Select t."OrderId",t."ProductCode",t."Quantity" From "OrderItem" t Where t."ProductCode" In (Select t1."Code" From "Product" t1 Where t1."Name" Like @p1)

Eager loading預先加載

  適用於SqlQuery.ToSingleAsync()及ToListAsync()。注意以下示例加載EntitySet屬性，會單獨生成Sql，所以不建議ToListAsync()時預先加載EntitySet屬性，更不建議嵌套預先加載EntitySet。

public async Task<object> Query()
{
    var q = new SqlQuery<Entities.Order>();
    q.Include(order => order.Customer)
        .ThenInclude(customer => customer.City)
     .Include(order => order.Items)
        .ThenInclude(item => item.Product);
    return await q.ToSingleAsync();
}

Select t."Id",t."CustomerId",j1."Id" "Customer.Id",j1."Name" "Customer.Name",j1."CityCode" "Customer.CityCode",j1."Phone" "Customer.Phone",j2."Code" "Customer.City.Code",j2."Name" "Customer.City.Name" From "Order" t Left Join "Customer" j1 On j1."Id"=t."CustomerId" Left Join "City" j2 On j2."Code"=j1."CityCode" Limit 1

Select t."OrderId",t."ProductCode",t."Quantity",j1."Code" "Product.Code",j1."Name" "Product.Name",j1."Unit" "Product.Unit" From "OrderItem" t Left Join "Product" j1 On j1."Code"=t."ProductCode" Where t."OrderId" = @p1

暫未實現Explicit loading(顯式加載);
暫不支持Lazy loading(延遲加載)

更新同時返回值 [2020-02-19更新]

  適用於扣減庫存同時返回扣減后的值，以判斷是否超出庫存數量。

public async Task Subtract(int itemId, int amount)
{
    using var conn = await DataStore.Default.OpenConnectionAsync();
    using var txn = conn.BeginTransaction();
    var upcmd = new SqlUpdateCommand<Entities.TestStocks>();
    upcmd.Update(t => t.Amount = t.Amount - amount);
    upcmd.Where(t => t.ItemId == itemId);
    //var outs = upcmd.Output(t => new { t.ItemId, t.Amount });
    var outs = upcmd.Output(t => t.Amount); //在下句執行前指定返回值
    await DataStore.Default.ExecCommandAsync(upcmd, txn); //顯式指定事務執行
    if (outs.Count != 1 || outs[0] < 0) //在執行后檢查返回結果
        throw new Exception("庫存不足");
    txn.Commit(); //成功遞交事務
}

Update "sys.TestStocks" t Set "Amount" = "Amount" + @p1 Where t."ItemId" = @p1 RETURNING "Amount"

小結

  GitHub上的運行時已更新可安裝測試，作者下一步重點是實現獨立的不依賴內置存儲的版本，並且實現模型包的導入與導出功能。另一邊碼代碼一邊碼文實屬不易，作者需要您的支持請您多多點贊推薦！