.NET ORM SqlSugar导航查询

时间:2022-06-03 果糖大数据科技人气:3

1、导航查询特点

作用：主要处理主对象里面有子对象这种层级关系查询

1.1 无外键开箱就用

其它ORM导航查询需要各种配置或者外键，而SqlSugar则开箱就用，无外键，只需配置特性和主键就能使用

1.2 高性能优

查询性能非常强悍

支持大数据分页导航查询

3.3 语法超级爽

注意：多级查询时VS有时候没提示直接写就行了，相比其他 .NET ORM语法要简单的多

var list=db.Queryable<Test>()
          .Includes(x => x.Provinces,x=>x.Citys ,x=>x.Street)//多级查询 有时候VS没提示手写
          .Includes(x => x.ClassInfo)// 一级查询
          .ToList();
                 
       //多级查询  加排序过滤
       .Includes(x =>x.Provinces.Where(z=>z.Id>0).OrderBy(z=>z.Id).ToList(),x=>x.Citys,x=>x.Street)
        // 一级查询
       .Includes(x =>x.ClassInfo)
       .ToList();

2、新导航查询 ORM

适合有主键的常规操作, 请升级到5.0.6.8

2.1 一对一

//实体
        public class StudentA
        {
            [SugarColumn(IsPrimaryKey = true, IsIdentity = true)]
            public int StudentId { get; set; }
            public string Name { get; set; }
            public int SchoolId { get; set; }
            [Navigate(NavigateType.OneToOne, nameof(SchoolId))]//一对一
            public SchoolA SchoolA { get; set; }
  
        }
        public class SchoolA
        {
            [SugarColumn(IsPrimaryKey = true, IsIdentity = true)]
            public int SchoolId { get; set; }
            public string SchoolName { get; set; } 
        }
//代码
 var list2 = db.Queryable<StudentA>()
           .Includes(x => x.SchoolA)
           .Where(x => x.SchoolA.SchoolName == "北大")//可以对一级导航进行过滤
           .ToList();

2.2 一对多

//实体
        public class StudentA
        {
            [SugarColumn(IsPrimaryKey = true, IsIdentity = true)]
            public int StudentId { get; set; }
            public string Name { get; set; }
            public int SchoolId { get; set; }
            [Navigate(NavigateType.OneToOne, nameof(SchoolId))]//一对一
            public SchoolA SchoolA { get; set; }
  
        }
        public class SchoolA
            public string SchoolName { get; set; } 
//代码
 var list2 = db.Queryable<StudentA>()
           .Includes(x => x.SchoolA)
           .Where(x => x.SchoolA.SchoolName == "北大")//可以对一级导航进行过滤
           .ToList();

2.3 多对多

//多对多
       public class ABMapping1
       {
            [SugarColumn(IsPrimaryKey = true )]
            public int AId { get; set; }
            [SugarColumn(IsPrimaryKey = true)]
            public int BId { get; set; }
        }
        public class A1
        {
            [SugarColumn(IsPrimaryKey = true, IsIdentity = true  )]
            public int Id { get; set; }
            public string Name { get; set; }
            [Navigate(typeof(ABMapping1),nameof(ABMapping1.AId),nameof(ABMapping1.BId))]
            public List<B1> BList { get; set; }
        }
        public class B1
        {
            [SugarColumn(IsPrimaryKey = true , IsIdentity = true)]
            public int Id { get; set; }
            public string Name { get; set; }
            [Navigate(typeof(ABMapping1), nameof(ABMapping1.BId), nameof(ABMapping1.AId))]
            public List<A1> AList { get; set; }
        }
 //例1:简单用法
var list3= db.Queryable<A1>().Includes(x => x.BList).ToList(); 
 
 //例2:支持子对象排序和过滤
var list3= db.Queryable<A1>().Includes(x => x.BList.Where(z=>z.Id>0).ToList()).ToList(); 
 
 //例3:支持主表过滤  Any和Count
var list3= db.Queryable<A1>().Includes(x => x.BList)
                             .Where(x=>x.BList .Any(z=>z.Id ==1)).ToList();

2.4 多级查询

配置好实体类，我们可以多级查询，.NET 中轻松多级查询

var list=db.Queryable<Test>()
               .Includes(x => x.Provinces,x=>x.Citys ,x=>x.Street)//有时候没提示 直接写
               .Includes(x => x.ClassInfo)// 一级查询
               .ToList();

2.5 大数据分页导航

适合一次性查询1000条以上的导航

var list = new List<Tree1>();
 
  db.Queryable<Tree1>()
      .Includes(it => it.Child)
      .ForEach(it => list.Add(it), 300); //每次查询300条

3、ORM无配置映射（高性能）

适合没有主键或者复杂的一些操作

3.1 无配置映射实现二层

结构: Student->SchoolA

var list = db.Queryable<StudentA>().ToList();
db.ThenMapper(list, stu =>
{
  //如果加Where不能带有stu参数，stu参数写到 SetContext
  stu.SchoolA=db.Queryable<SchoolA>().SetContext(scl=>scl.SchoolId,()=>stu.SchoolId,stu).FirstOrDefault();
});
// SetContext不会生成循环操作，高性能  和直接Where性能是不一样的

如果没有SetContext那么这个查询将会循环

3.2 无配置映射无限级

了解原理后我们用ThenMapper想映射哪层就映射哪层

var treeRoot=db.Queryable<Tree>().Where(it => it.Id == 1).ToList();
//第一层
db.ThenMapper(treeRoot, item =>
{
    item.Child = db.Queryable<Tree>().SetContext(x => x.ParentId, () => item.Id, item).ToList();
});
//第二层
db.ThenMapper(treeRoot.SelectMany(it=>it.Child), it =>
{
    it.Child = db.Queryable<Tree>().SetContext(x => x.ParentId, () => it.Id, it).ToList();
});
//第三层
db.ThenMapper(treeRoot.SelectMany(it => it.Child).SelectMany(it=>it.Child), it =>
{
    it.Child = db.Queryable<Tree>().SetContext(x => x.ParentId, () => it.Id, it).ToList();
});
//这儿只是用树型结构来证明可以实现无限级别导航查询 ,实际开发中树型结构用ToTree实现
public class Tree
{
[SqlSugar.SugarColumn(IsPrimaryKey =true)]
public int Id { get; set; }
public string Name { get; set; }
public int ParentId { get; set; }
[SqlSugar.SugarColumn(IsIgnore = true)]
public Tree Parent { get; set; }
[SqlSugar.SugarColumn(IsIgnore = true)]
public List<Tree> Child { get; set; }
}
// SetContext不会生成循环操作，高性能  和直接Where性能是不一样的

4 、.NET ORM 未来计划

Json to sql 正在开发中，未来将打造一套直接由前端操作数据库的API

{
"Queryable":"order",
 Select:[ [{SqlFunc_AggregateMin:["id"]},"id"], [{SqlFunc_GetDate:[]},"Date"] ]
}

将支持权限过滤，验证，多表查询，层级导航查询等　　

GitHUB 源码：

https://github.com/donet5/SqlSugar

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