EFCore pgsql Join 查询

安装包

   > Microsoft.EntityFrameworkCore              6.0.35   6.0.35
   > Microsoft.EntityFrameworkCore.Tools        6.0.35   6.0.35
   > Npgsql.EntityFrameworkCore.PostgreSQL      6.0.29   6.0.29

定义实体等


using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;

namespace EFCoreJoinQuery
{
    public class EFCoreHelperDbContext:DbContext
    {
        public EFCoreHelperDbContext(DbContextOptions<EFCoreHelperDbContext> options):base(options)
        {

        }

        public DbSet<Student> Students { get; set; }

        public DbSet<School> Schools { get; set;}

        public DbSet<StudentHobby> StudentHobbys { get;set; }


        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.HasDefaultSchema("ellis"); //因为这里我是将表生成到这个schema
            base.OnModelCreating(modelBuilder);
            modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);  
        }
    }




    public class School
    {
        public int SchoolId { get; set; }

        public string Name { get; set; }
    }


    public class SchoolConfig : IEntityTypeConfiguration<School>
    {
        public void Configure(EntityTypeBuilder<School> builder)
        {
            builder.ToTable("school");
            builder.HasKey(x => x.SchoolId);
            builder.Property(x => x.Name).IsRequired().HasColumnName("name");
            builder.Property(x=>x.SchoolId).HasColumnName("school_id").ValueGeneratedOnAdd();
        }
    }

    public class Student
    {
        public int StudentId { get; set;}

        public string Name { get; set; }

        public int SchoolId { get; set; }
    }


    public class StudentConfig : IEntityTypeConfiguration<Student>
    {
        public void Configure(EntityTypeBuilder<Student> builder)
        {
            builder.ToTable("student");
            builder.HasKey(x => x.StudentId);
            builder.Property(x => x.Name).IsRequired().HasColumnName("name");
            builder.Property(x => x.SchoolId).HasColumnName("school_id");
            builder.Property(x => x.StudentId).HasColumnName("student_id").ValueGeneratedOnAdd();
        }
    }

    public class StudentHobby
    {
        public int HobbyId { get; set; }

        public string Name { get; set; }

        public int StudentId { get; set; }

    }

    public class StudentHobbyConfig : IEntityTypeConfiguration<StudentHobby>
    {
        public void Configure(EntityTypeBuilder<StudentHobby> builder)
        {
            builder.ToTable("student_hobby");
            builder.HasKey(x => x.HobbyId);
            builder.Property(x=>x.Name).IsRequired().HasColumnName("name");
            builder.Property(x => x.StudentId).HasColumnName("student_id");
            builder.Property(x => x.HobbyId).HasColumnName("hobby_id").ValueGeneratedOnAdd();
        }
    }
}

这里需要说明的是需要配置MigrationsHistoryTable，因为我这里是将表迁移到ellis这个schema，所以迁移的历史表也需要创建到这个schema中

builder.Services.AddDbContext<EFCoreHelperDbContext>((sp, options) =>
{
    options.UseNpgsql("Host=192.168.214.133;Port=32222;Database=postgresdb;Username=postgresadmin;Password=admin123;SearchPath=ellis;",x=>x.MigrationsHistoryTable(HistoryRepository.DefaultTableName,"ellis"))
    .LogTo(Console.WriteLine, new[] { DbLoggerCategory.Database.Command.Name }, LogLevel.Information)
                   .EnableSensitiveDataLogging();
});

迁移

add-migration ellis
update-databse ellis

controller使用

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace EFCoreJoinQuery.Controllers
{
    [Route("api/[controller]/[action]")]
    [ApiController]
    public class JoinController : ControllerBase
    {
        private readonly EFCoreHelperDbContext _eFCoreHelperDbContext;

        public JoinController(EFCoreHelperDbContext eFCoreHelperDbContext)
        {
            _eFCoreHelperDbContext = eFCoreHelperDbContext;
        }

		//两张表
        [HttpGet]
        public async  Task<IActionResult> Query2Join()
        {
            // 单列Join
            var value = from s in _eFCoreHelperDbContext.Schools
                        join st in _eFCoreHelperDbContext.Students
                        on s.SchoolId equals st.SchoolId
                        select new 
                        { 
                            SchoolName = s.Name, 
                            StudentName = st.Name
                        };

            //多列Join
            //on        new { m1.field1, m1.field2 }
            //      equals new { m2.field1, m2.field2 }
            return Ok(value);
        }

		//三张表
        [HttpGet]

        public async Task<IActionResult> Query3Join()
        {
            var value = from s in _eFCoreHelperDbContext.Schools
                        join st in _eFCoreHelperDbContext.Students
                        on s.SchoolId equals st.SchoolId
                        join h in _eFCoreHelperDbContext.StudentHobbys
                        on st.StudentId equals  h.StudentId
                        //因为hobby是多个，这里需要分组一次
                        group h by new { schollName = s.Name,studentName = st.Name } into grouped
                        select new
                        {
                            SchoolName = grouped.Key.schollName,
                            StudentName = grouped.Key.studentName,
                            HobbyNames = string.Join(", ", grouped.Select(g => g.Name))
                        };
            return Ok(value);
        }
    }
}

https://www.tektutorialshub.com/entity-framework-core/join-query-in-ef-core/

EFCore pgsql Join 查询

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