Can someone Turn this group by code into Pomelo Entity Framework? - sql

Question

I'm trying to get the number of tasks performed on a daily basis and plot them into a chart, but the thing is I can't figure out the pomelo entity code.
Select FirstName,count(ToDoId)
From todos as M
Inner join users as u
on M.UserId=u.UserId
where u.UserId=1
GROUP BY M.UserId, CAST(M.CreatedAt AS DATE)

Answer 1

Assuming corresponding model classes for your two tables, that contain navigation properties, the LINQ query could look like this:
var todoCountByFirstNameAndDate = context.Todos.Include(e => e.User)
.GroupBy(t => new {t.User.FirstName, t.CreatedAt.Date})
.Select(g => new {g.Key.FirstName, g.Key.Date, TodoCount = g.Count()})
.ToList();
The generated SQL would then be:
SELECT `u`.`FirstName`, CONVERT(`t`.`CreatedAt`, date) AS `Date`, COUNT(*) AS `TodoCount`
FROM `Todos` AS `t`
INNER JOIN `Users` AS `u` ON `t`.`UserId` = `u`.`UserId`
GROUP BY `u`.`FirstName`, CONVERT(`t`.`CreatedAt`, date)
Here is a complete and working console sample project, that demonstrates the bits and pieces:
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using Pomelo.EntityFrameworkCore.MySql.Infrastructure;
namespace IssueConsoleTemplate
{
//
// Entities:
//
public class User
{
public int UserId { get; set; }
public string FirstName { get; set; }
public virtual ICollection<Todo> Todos { get; set; } = new HashSet<Todo>();
}
public class Todo
{
public int TodoId { get; set; }
public DateTime CreatedAt { get; set; }
public int UserId { get; set; }
public User User { get; set; }
}
//
// DbContext:
//
public class Context : DbContext
{
public DbSet<User> Users { get; set; }
public DbSet<Todo> Todos { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder
.UseMySql(
"server=127.0.0.1;port=3306;user=root;password=;database=So67149928",
b => b.ServerVersion("8.0.21-mysql")
.CharSetBehavior(CharSetBehavior.NeverAppend))
.UseLoggerFactory(
LoggerFactory.Create(
b => b
.AddConsole()
.AddFilter(level => level >= LogLevel.Information)))
.EnableSensitiveDataLogging()
.EnableDetailedErrors();
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<User>()
.HasData(
new User {UserId = 1, FirstName = "John"},
new User {UserId = 2, FirstName = "Jane"});
modelBuilder.Entity<Todo>()
.HasData(
new Todo {TodoId = 11, CreatedAt = new DateTime(2021, 4, 17, 14, 21, 41), UserId = 1},
new Todo {TodoId = 12, CreatedAt = new DateTime(2021, 4, 17, 18, 11, 21), UserId = 1},
new Todo {TodoId = 13, CreatedAt = new DateTime(2021, 4, 17, 14, 21, 41), UserId = 2},
new Todo {TodoId = 14, CreatedAt = new DateTime(2021, 4, 18, 18, 11, 21), UserId = 2});
}
}
internal static class Program
{
private static void Main()
{
using var context = new Context();
context.Database.EnsureDeleted();
context.Database.EnsureCreated();
var todoCountByFirstNameAndDate = context.Todos.Include(e => e.User)
.GroupBy(t => new {t.User.FirstName, t.CreatedAt.Date})
.Select(g => new {g.Key.FirstName, g.Key.Date, TodoCount = g.Count()})
.OrderBy(r => r.FirstName)
.ThenBy(r => r.Date)
.ToList();
Trace.Assert(todoCountByFirstNameAndDate.Count == 3);
Trace.Assert(todoCountByFirstNameAndDate[0].FirstName == "Jane");
Trace.Assert(todoCountByFirstNameAndDate[0].Date == new DateTime(2021, 4, 17));
Trace.Assert(todoCountByFirstNameAndDate[0].TodoCount == 1);
Trace.Assert(todoCountByFirstNameAndDate[1].FirstName == "Jane");
Trace.Assert(todoCountByFirstNameAndDate[1].Date == new DateTime(2021, 4, 18));
Trace.Assert(todoCountByFirstNameAndDate[1].TodoCount == 1);
Trace.Assert(todoCountByFirstNameAndDate[2].FirstName == "John");
Trace.Assert(todoCountByFirstNameAndDate[2].Date == new DateTime(2021, 4, 17));
Trace.Assert(todoCountByFirstNameAndDate[2].TodoCount == 2);
}
}
}