实体框架：如何一次查询数据库中的多个相关表

Question

我有一个查询目前太慢了。 我正在尝试在主页上搜索一个代码（一个字符串），它将为用户带来相关信息。 例如。用户可以从主页搜索代码，这将在 Job、Work Phase、Wbs、Work Element、EA、Jobcard 和 Estimate 中搜索代码并返回相关信息。 当我相信可以一次完成时，我会多次访问数据库来收集我需要的数据。 我有许多链接的表： 合同、工作、工作阶段、Wbss、工程活动、工作卡和估算。 合同有一份工作清单， 作业有一个工作阶段列表， 工作阶段有一个 Wbss 等列表

有更快的方法吗？

public Result Handle(Query query)
{                   
    query.Code = query.Code ?? string.Empty;

    var result = new Result();

    //result.SetParametersFromPagedQuery(query);
    result.Items = new List<Item>();

    if (query.SearchPerformed)
    {
        var contracts = _db.Contracts.AsEnumerable().Where(x => x.Code == query.Code);

        result.Items = result.Items.Concat(contracts.Select(x => new Item()
        {
            Code = x.Code,
            Id = x.Id,
            Name = x.Name,
            Type = MainPageSearchEnum.Contract,
            ContractName = x.Name,
            Url = string.Format("Admin/Contract/Edit/{0}", x.Id)
        })).ToList();


        var jobs = _db.Jobs.AsEnumerable().Where(x => x.Code == query.Code);

        result.Items = result.Items.Concat(jobs.Select(x => new Item()
        {
            Code = x.Code,
            Id = x.Id,
            Name = x.Name,
            ContractName = x.Contract.Name,
            Type = MainPageSearchEnum.Job,
            Url = string.Format("Admin/Job/Edit/{0}", x.Id)
        })).ToList();

        //var workPhases = _db.WorkPhases.AsEnumerable().Where(x => x.ContractPhase.Code.ToLower() == query.Code.ToLower());
        var workPhases = _db.WorkPhases.AsEnumerable().Where(x => x.ContractPhase.Code == query.Code);

        result.Items = result.Items.Concat(workPhases.Select(x => new Item()
        {
            Code = x.ContractPhase.Code,
            Id = x.Id,
            Name = x.ContractPhase.Name,
            Type = MainPageSearchEnum.WorkPhase,
            Url = string.Format("Admin/WorkPhase/Edit/{0}", x.Id)
        })).ToList();

        var wbss = _db.WBSs.AsEnumerable().Where(x => x.Code == query.Code);

        result.Items = result.Items.Concat(wbss.Select(x => new Item()
        {
            Code = x.Code,
            Id = x.Id,
            Name = x.Name,
            Type = MainPageSearchEnum.WBS,
            Url = string.Format("Admin/WBS/Edit/{0}", x.Id)
        })).ToList();

        var eas = _db.EngineeringActivities.AsEnumerable().Where(x => x.Code == query.Code);

        result.Items = result.Items.Concat(eas.Select(x => new Item()
        {
            Code = x.Code,
            Id = x.Id,
            Name = x.Name,
            Type = MainPageSearchEnum.EA,
            Url = string.Format("Admin/EngineeringActivity/Edit/{0}", x.Id)
        })).ToList();

        var jcs = _db.Jobcards.AsEnumerable().Where(x => x.Code == query.Code);

        result.Items = result.Items.Concat(jcs.Select(x => new Item()
        {
            Code = x.Code,
            Id = x.Id,
            Name = x.Name,
            Type = MainPageSearchEnum.EA,
            Url = string.Format("Admin/JobCard/Edit/{0}", x.Id)
        })).ToList();

        var estimates = _db.Estimates.AsEnumerable().Where(x => x.Code == query.Code);

        result.Items = result.Items.Concat(estimates.Select(x => new Item()
        {
            Code = x.Code,
            Id = x.Id,
            Name = x.Name,
            Type = MainPageSearchEnum.Estimate,
            Url = string.Format("Estimation/Estimate/Edit/{0}", x.Id)
        })).ToList();

    }

    return result;
}

Answer 1

免责声明：我是项目的所有者Entity Framework Plus

此库具有 Query Future 功能，允许在一次往返中批量处理多个查询。

例子：

// using Z.EntityFramework.Plus; // Don't forget to include this.
var ctx = new EntitiesContext();

// CREATE a pending list of future queries
var futureCountries = ctx.Countries.Where(x => x.IsActive).Future();
var futureStates = ctx.States.Where(x => x.IsActive).Future();

// TRIGGER all pending queries in one database round trip
// SELECT * FROM Country WHERE IsActive = true;
// SELECT * FROM State WHERE IsActive = true
var countries = futureCountries.ToList();

// futureStates is already resolved and contains the result
var states = futureStates.ToList();

维基：EF+ Query Future

Answer 2

您尝试过Union / UnionAll 运算符吗？

其目的与您的愿望完全一样 - 将来自不同来源的相同数据组合在一起。

此外，由于 deferred execution 的概念，您的查询只会在您实际迭代结果时执行（或调用执行此操作的方法，例如 - .ToList()

var contractsQuery = _db.Contracts.AsEnumerable().Where(x => x.Code == query.Code).Select(x=>new {Code=x.Code, Id=x.Id, ...});
var jobsQuery = _db.Jobs.AsEnumerable().Where(x => x.Code == query.Code).Select(x=>new{Code=x.Code, Id=x.Id, ...});
var workPhasesQuery = _db.WorkPhases.AsEnumerable().Where(x => x.ContractPhase.Code == query.Code).Select(x=>new{Code=x.Code, Id=x.Id, ...});
    // and so on
var combinedQuery = contractsQuery.UnionAll(jobsQuery).UnionAll(workPhasesQuery ).UnionAll(...
var result = combinedQuery.ToList();

类似的问题是Union in linq entity framework
另一个代码示例可以找到here

请注意，这与 T-SQL union 中操作数据的概念完全相同，并且在幕后您将使用 union 运算符获得 sql 查询

Answer 3

是的，肯定有一种查询多个表的方法。您可以使用Include() 方法扩展进行查询。例如：

var examplelist = _db.Contracts.(v => v.id == "someid" && v.name == "anotherfilter").Include("theOtherTablesName").ToList();

您可以通过这种方式添加任意数量的表格。这是推荐的方法。

您也可以使用UnionAll() 方法，但您必须为此单独定义查询