02020406 EF Core基础06-EF Core生成的SQL
1. 通过代码查看EF Core的SQL语句（视频3-12）
1.1 方法1：标准日志
// 标准日志用法示例
public static readonly ILoggerFactory MyLoggerFactory= LoggerFactory.Create(builder => { builder.AddConsole(); });optionsBuilder.UseLoggerFactory(MyLoggerFactory);
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// 需要安装的包
1. microsoft.entityframeworkcore.sqlserver -Version 5.0.4
2. microsoft.entityframeworkcore.tools -Version 5.0.4
3. install-package microsoft.extensions.logging.console -version 5.0.0
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// Dog.cs
namespace DBLogDemo
{public class Dog{public long Id { get; set; }public string Name { get; set; }}
}
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// DbContext.cs
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;namespace DBLogDemo
{class MyDbContext : DbContext{private static ILoggerFactory loggerFactory = LoggerFactory.Create(b => b.AddConsole()); // @1public DbSet<Dog> Dogs { get; set; }protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder){string connStr = "Server=.;Database=CoreDataDB;Trusted_Connection=True;MultipleActiveResultSets=true";optionsBuilder.UseSqlServer(connStr);optionsBuilder.UseLoggerFactory(loggerFactory); // @2}protected override void OnModelCreating(ModelBuilder modelBuilder){base.OnModelCreating(modelBuilder);modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);}}
}
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using System;
using System.Threading.Tasks;namespace DBLogDemo
{class Program{static async Task Main(string[] args){using (MyDbContext ctx = new MyDbContext()){Dog d01 = new Dog();d01.Name = "abc";ctx.Dogs.Add(d01);await ctx.SaveChangesAsync();d01.Name = "abc";Console.WriteLine(d01.Id);}Console.ReadLine();}}
}控制台输出：
info: Microsoft.EntityFrameworkCore.Infrastructure[10403]Entity Framework Core 5.0.4 initialized 'MyDbContext' using provider 'Microsoft.EntityFrameworkCore.SqlServer' with options: None
info: Microsoft.EntityFrameworkCore.Database.Command[20101]Executed DbCommand (31ms) [Parameters=[@p0='?' (Size = 4000)], CommandType='Text', CommandTimeout='30']SET NOCOUNT ON; // 标准SQL语句startINSERT INTO [Dogs] ([Name])VALUES (@p0);SELECT [Id]FROM [Dogs]WHERE @@ROWCOUNT = 1 AND [Id] = scope_identity(); // 标准SQL语句end
2 // Id值
1.2 方法2：简单日志
// 简单日志用法示例
optionsBuilder.LogTo(Console.WriteLine);
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// 需要安装的包
1. microsoft.entityframeworkcore.sqlserver -version 5.0.4
2. microsoft.entityframeworkcore.tools -version 5.0.4
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// Dog.cs
namespace DBLogDemo
{public class Dog{public long Id { get; set; }public string Name { get; set; }}
}
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// DbContext.cs
using Microsoft.EntityFrameworkCore;namespace DBLogDemo
{class MyDbContext : DbContext{public DbSet<Dog> Dogs { get; set; }protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder){string connStr = "Server=.;Database=CoreDataDB;Trusted_Connection=True;MultipleActiveResultSets=true";optionsBuilder.UseSqlServer(connStr);optionsBuilder.LogTo( msg => {System.Console.WriteLine(msg);}); // LogTo参数为string形式的委托}protected override void OnModelCreating(ModelBuilder modelBuilder){base.OnModelCreating(modelBuilder);modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);}}
}
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// Program.cs
using System;
using System.Threading.Tasks;namespace DBLogDemo
{class Program{static async Task Main(string[] args){using (MyDbContext ctx = new MyDbContext()){Dog d01 = new Dog();d01.Name = "abc";ctx.Dogs.Add(d01);await ctx.SaveChangesAsync();d01.Name = "abc";Console.WriteLine(d01.Id);}Console.ReadLine();}}
}控制台输出：
info: 2025/9/21 20:38:14.997 CoreEventId.ContextInitialized[10403] (Microsoft.EntityFrameworkCore.Infrastructure)
...SaveChanges completed for 'MyDbContext' with 1 entities written to the database.
3 // Id值
dbug: 2025/9/21 20:38:15.510 CoreEventId.ContextDisposed[10407] (Microsoft.EntityFrameworkCore.Infrastructure)'MyDbContext' disposed.说明：
1. 用起来简单，但是看起来好多啊-_-。
2. 可以输出EF Core整个生命周期的日志信息。
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// DbContext.cs
using Microsoft.EntityFrameworkCore;namespace DBLogDemo
{class MyDbContext : DbContext{public DbSet<Dog> Dogs { get; set; }protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder){string connStr = "Server=.;Database=CoreDataDB;Trusted_Connection=True;MultipleActiveResultSets=true";optionsBuilder.UseSqlServer(connStr);optionsBuilder.LogTo( msg => { if (!msg.Contains("CommandExecuting")) return; System.Console.WriteLine(msg);}); // 过滤信息，只要SQL语句部分。}protected override void OnModelCreating(ModelBuilder modelBuilder){base.OnModelCreating(modelBuilder);modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);}}
}
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// Program.csusing System;
using System.Threading.Tasks;namespace DBLogDemo
{class Program{static async Task Main(string[] args){using (MyDbContext ctx = new MyDbContext()){Dog d01 = new Dog();d01.Name = "abc";ctx.Dogs.Add(d01);await ctx.SaveChangesAsync();d01.Name = "abc";Console.WriteLine(d01.Id);}Console.ReadLine();}}
}控制台输出：
dbug: 2025/9/21 20:46:21.950 RelationalEventId.CommandExecuting[20100] (Microsoft.EntityFrameworkCore.Database.Command)Executing DbCommand [Parameters=[@p0='?' (Size = 4000)], CommandType='Text', CommandTimeout='30']SET NOCOUNT ON;INSERT INTO [Dogs] ([Name])VALUES (@p0);SELECT [Id]FROM [Dogs]WHERE @@ROWCOUNT = 1 AND [Id] = scope_identity();
5说明：只输出SQL语句部分。
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// Program.cs，演示多条SQL语句。
using System;
using System.Linq;
using System.Threading.Tasks;namespace DBLogDemo
{class Program{static async Task Main(string[] args){using (MyDbContext ctx = new MyDbContext()){Dog d01 = new Dog();d01.Name = "abc";ctx.Dogs.Add(d01); // SQL语句1ctx.Dogs.Add(new Dog { Name = "Trump" }); // SQL语句2await ctx.SaveChangesAsync();Console.WriteLine(ctx.Dogs.Count()); // SQL语句3}Console.ReadLine();}}
}控制台输出：
dbug: 2025/9/21 20:52:51.558 RelationalEventId.CommandExecuting[20100] (Microsoft.EntityFrameworkCore.Database.Command)Executing DbCommand [Parameters=[@p0='?' (Size = 4000)], CommandType='Text', CommandTimeout='30']SET NOCOUNT ON;INSERT INTO [Dogs] ([Name])VALUES (@p0);SELECT [Id]FROM [Dogs]WHERE @@ROWCOUNT = 1 AND [Id] = scope_identity();
dbug: 2025/9/21 20:52:51.624 RelationalEventId.CommandExecuting[20100] (Microsoft.EntityFrameworkCore.Database.Command)Executing DbCommand [Parameters=[@p0='?' (Size = 4000)], CommandType='Text', CommandTimeout='30']SET NOCOUNT ON;INSERT INTO [Dogs] ([Name])VALUES (@p0);SELECT [Id]FROM [Dogs]WHERE @@ROWCOUNT = 1 AND [Id] = scope_identity();
dbug: 2025/9/21 20:52:51.854 RelationalEventId.CommandExecuting[20100] (Microsoft.EntityFrameworkCore.Database.Command)Executing DbCommand [Parameters=[], CommandType='Text', CommandTimeout='30']SELECT COUNT(*)FROM [Dogs] AS [d]说明：过滤后每个SQL操作的语句都可以查到，如果SQL操作很多，那么输出很多个SQL语句，查起来会很麻烦。可以定向的找到所需要的SQL语句。
1.3 方法3：ToQueryString
1、上面两种方式无法直接得到一个操作的SQL语句，而且在操作很多的情况下，容易混乱。
2、EF Core的Where方法返回的是IQueryable类型，DbSet也实现了IQueryable接口。 IQueryable有扩展方法ToQueryString()可以获得SQL。
3、不需要真的执行查询才获取SQL语句；只能获取查询操作的。
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
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// Dog.cs
namespace DBLogDemo
{public class Dog{public long Id { get; set; } //主键public string Name { get; set; }//标题}
}
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// MyDbContext
using Microsoft.EntityFrameworkCore;namespace DBLogDemo
{class MyDbContext : DbContext{public DbSet<Dog> Dogs { get; set; }protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder){string connStr = "Server=.;Database=CoreDataDB;Trusted_Connection=True;MultipleActiveResultSets=true";optionsBuilder.UseSqlServer(connStr);}protected override void OnModelCreating(ModelBuilder modelBuilder){base.OnModelCreating(modelBuilder);modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);}}
}
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using Microsoft.EntityFrameworkCore;
using System;
using System.Linq;
using System.Threading.Tasks;namespace DBLogDemo
{class Program{static async Task Main(string[] args){using (MyDbContext ctx = new MyDbContext()){Dog d01 = new Dog();d01.Name = "abc";ctx.Dogs.Add(d01);ctx.Dogs.Add(new Dog { Name = "Trump" }); // 拿不到await ctx.SaveChangesAsync();Console.WriteLine(ctx.Dogs.Count()); // 拿不到IQueryable<Dog> dogs01 = ctx.Dogs.Where(d => d.Name.ToLower() == "Trump");string sql = dogs01.ToQueryString();Console.WriteLine("这就是我要的SQL语句：" + sql); // ToQueryStirng只能拿到查询操作的SQL语句/*foreach (var it in d02){Console.WriteLine(it.Id);}*/}Console.ReadLine();}}
}控制台输出：
13
SELECT [d].[Id], [d].[Name]
FROM [Dogs] AS [d]
WHERE LOWER([d].[Name]) = N'Trump'说明：
1. ToQueryString方法只能拿到查询操作的SQL语句，其它形式的SQL语句拿不到。
2. ToQueryString方法可以在不真的执行数据库查询的情形下直接拿到查询结果，后续课程会演示。
1.4 总结
- 写测试性代码，用简单日志；
- 正式需要记录SQL给审核人员或者排查故障，用标准日志；
- 开发阶段，从繁杂的查询操作中立即看到SQL，用ToQueryString()。
2. 同样的LINQ被翻译为不同的SQL语句（视频3-13）
- 本课跳过，目前只针对性的学习SQL Server。本机也没安装其它数据库，无法演示。
- 后续用得到再补。
结尾
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视频：https://www.bilibili.com/video/BV1pK41137He
著：杨中科
ISBN：978-7-115-58657-5
版次：第1版
发行：人民邮电出版社
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