自研ORM 子查询&嵌套查询

作者 Mr-zhong

代码改变世界....

一、前言

Fast Framework 基于NET6.0 封装的轻量级 ORM 框架 支持多种数据库 SqlServer Oracle MySql PostgreSql Sqlite

优点： 体积小、可动态切换不同实现类库、原生支持微软特性、流畅API、使用简单、性能高、模型数据绑定采用 委托、强大的表达式解析、支持多种子查询可实现较为复杂查询、源代码可读性强。

缺点：目前仅支持Db Frist Code Frist 后续迭代。

开源地址：https://github.com/China-Mr-zhong/Fast-Framework （唯一）

更多示例：https://www.cnblogs.com/China-Mr-zhong/p/17514567.html

• 导航查询

  • 示例代码

                    /// <summary>
                    /// 类别
                    /// </summary>
                    public class Category
                    {
                        /// <summary>
                        /// 类别ID
                        /// </summary>
                        [Key]
                        public int CategoryId { get; set; }
    
                        /// <summary>
                        /// 类别名称
                        /// </summary>
                        public string CategoryName { get; set; }
    
                        /// <summary>
                        /// 产品 Navigate MainName和ChildName 可不显示指定，会自动查找主键匹配或ID为结尾的属性
                        /// </summary>
                        [Navigate(MainName = nameof(CategoryId), ChildName = nameof(Product.CategoryId))]
                        public IEnumerable<Product> Products { get; set; }
    
                    }
    
                    var data = db.Query<Category>()
                        .Include(i => i.Products)
                        .ToList();
    

  • 执行后Sql

    SELECT Include_A.`CategoryId`,Include_A.`CategoryName`,Include_B.`ProductId`,Include_B.`ProductCode`,Include_B.`ProductName`,Include_B.`DeleteMark`,Include_B.`CreateTime`,Include_B.`ModifyTime`,Include_B.`Custom1`,Include_B.`Custom2`,Include_B.`Custom3`,Include_B.`Custom4`,Include_B.`Custom5`,Include_B.`Custom6`,Include_B.`Custom7`,Include_B.`Custom8`,Include_B.`Custom9`,Include_B.`Custom10`,Include_B.`Custom11`,Include_B.`Custom12` FROM `Category` `Include_A`
    INNER JOIN `Product` `Include_B` ON `Include_A`.`CategoryId` = `Include_B`.`CategoryId`
    

• Join子查询

  • 示例代码

                    var subQuery1 = db.Query<Product>().Select(s => new
                    {
                        s.ProductId,
                        s.CategoryId,
                        s.ProductCode,
                        s.ProductName,
                        s.DeleteMark
                    });
                    var data = db.Query<Category>().InnerJoin(subQuery1, (a, b) => a.CategoryId == b.CategoryId).ToList();
    

  • 执行后Sql

    SELECT p1.`CategoryId`,p1.`CategoryName`,p2.`ProductId`,p2.`ProductCode`,p2.`ProductName`,p2.`DeleteMark` FROM `Category` `p1`
    INNER JOIN ( SELECT `ProductId` AS `ProductId`,`CategoryId` AS `CategoryId`,`ProductCode` AS `ProductCode`,`ProductName` AS `ProductName`,`DeleteMark` AS `DeleteMark` FROM `Product` ) `p2` ON ( `p1`.`CategoryId` = `p2`.`CategoryId` )
    

• From子查询

  • 示例代码

                    var subQuery2 = db.Query<Product>().Select(s=>new
                    {
                        s.ProductId,
                        s.CategoryId,
                        s.ProductCode,
                        s.ProductName,
                        s.DeleteMark
                    });
                    var data = db.Query(subQuery2).ToList();
    

  • 执行后Sql

    SELECT * FROM ( SELECT `ProductId` AS `ProductId`,`CategoryId` AS `CategoryId`,`ProductCode` AS `ProductCode`,`ProductName` AS `ProductName`,`DeleteMark` AS `DeleteMark` FROM `Product` ) x
    

• Select子查询

  • 示例代码

                    var data = db.Query<Product>().Select(s => new
                    {
                        CategoryName = db.Query<Category>().Where(w => w.CategoryId == 1).Select(s => s.CategoryName).First()
                    }).First();
    

  • 执行后Sql

    SELECT ( SELECT `p2`.`CategoryName` FROM `Category` `p2`
    WHERE ( `p2`.`CategoryId` = 1 ) Limit 1 ) AS `CategoryName` FROM `Product` `p1` Limit 1
    

• Select嵌套查询

  • 示例代码

    var data1 = db.Query<Product>().Select(s => new
                    {
                        NestedQuery = db.Query<Category>().Where(w => w.CategoryId == s.CategoryId).ToList()
                    }).First();
    
                    var data2 = db.Query<Product>().Where(w => w.ProductId == 1).Select(s => new
                    {
                        NestedQuery = db.Query<Category>().Where(w => w.CategoryId == s.CategoryId).ToList()
                    }).First();
    

  • 执行后Sql

    //内部机制主查询有结果才执行嵌套查询，懒加载实现
    
    SELECT 0 AS `fast_args_index_0` FROM `Product` `p1` Limit 1
    
    --------------------------------------------------------------------------
    
    SELECT p2.`CategoryId`,p2.`CategoryName`,p1.`ProductId`,p1.`ProductCode`,p1.`ProductName`,p1.`DeleteMark`,p1.`CreateTime`,p1.`ModifyTime`,p1.`Custom1`,p1.`Custom2`,p1.`Custom3`,p1.`Custom4`,p1.`Custom5`,p1.`Custom6`,p1.`Custom7`,p1.`Custom8`,p1.`Custom9`,p1.`Custom10`,p1.`Custom11`,p1.`Custom12` FROM `Category` `p2`
    RIGHT JOIN `Product` `p1` ON ( `p2`.`CategoryId` = `p1`.`CategoryId` )
    
    SELECT 0 AS `fast_args_index_0` FROM `Product` `p1`
    WHERE ( `p1`.`ProductId` = 1 ) Limit 1
    

• Where子查询

  • 示例代码

                    var data = db.Query<Category>().Where(w => w.CategoryId == 1 && db.Query<Product>().Where(w => w.CategoryId == 1).Select(s => 1).Any()).First();//Any支持取反
    

  • 执行后Sql

    SELECT p1.`CategoryId`,p1.`CategoryName` FROM `Category` `p1`
    WHERE ( ( `p1`.`CategoryId` = 1 ) AND EXISTS ( SELECT 1 FROM `Product` `p2`
    WHERE ( `p2`.`CategoryId` = 1 ) ) ) Limit 1