https://stackoverflow.com/questions/67590678/runtime-type-error-in-f-linq-sql-query-with-group-by-on-multiple-columns

Program.fs

open System
open System.Linq
open FSharp.Data.TypeProviders
open Microsoft.FSharp.Linq.RuntimeHelpers

type Db = SqlDataConnection<"Server=.;Database=QueryTest;Trusted_Connection=true">
let d = Db.GetDataContext()

type Result =
    {
        pkey : int
        lphasekey : Nullable<int>
        orgk : int
        time : int
    }

let test vDate bDate =

    let q =
        query {
            for row1 in d.Table1 do
            where (row1.Date >= vDate)
            where (row1.Date <= bDate)
            join row2 in d.Table2 on
                (row1.Table2Key = row2.Table2Key)
            let key = AnonymousObject<int,int,Nullable<int>>(row1.Table3Key,row1.ProjectTableKey,row2.ProjectPhaseKey)
            where row2.ProjectPhaseKey.HasValue
            groupValBy row1 key into g
            select
                {
                    pkey = g.Key.Item2
                    lphasekey = g.Key.Item3
                    orgk = g.Key.Item1
                    time = g.Sum (fun x -> x.Data)
                }
        }

    for value in q do
        printfn "%A" value

[<EntryPoint>]
let main argv =
    test
        (DateTime.Parse "5/1/2021")
        (DateTime.Parse "6/1/2021")
    0

Schema.sql

USE [master]
GO
/****** Object:  Database [QueryTest]    Script Date: 5/18/2021 3:37:20 PM ******/
CREATE DATABASE [QueryTest]
 CONTAINMENT = NONE
 ON  PRIMARY 
( NAME = N'QueryTest', FILENAME = N'D:\Data\SQL Server\Databases\QueryTest.mdf' , SIZE = 8192KB , MAXSIZE = UNLIMITED, FILEGROWTH = 65536KB )
 LOG ON 
( NAME = N'QueryTest_log', FILENAME = N'D:\Data\SQL Server\Databases\QueryTest_log.ldf' , SIZE = 8192KB , MAXSIZE = 2048GB , FILEGROWTH = 65536KB )
GO
ALTER DATABASE [QueryTest] SET COMPATIBILITY_LEVEL = 140
GO
IF (1 = FULLTEXTSERVICEPROPERTY('IsFullTextInstalled'))
begin
EXEC [QueryTest].[dbo].[sp_fulltext_database] @action = 'enable'
end
GO
ALTER DATABASE [QueryTest] SET ANSI_NULL_DEFAULT OFF 
GO
ALTER DATABASE [QueryTest] SET ANSI_NULLS OFF 
GO
ALTER DATABASE [QueryTest] SET ANSI_PADDING OFF 
GO
ALTER DATABASE [QueryTest] SET ANSI_WARNINGS OFF 
GO
ALTER DATABASE [QueryTest] SET ARITHABORT OFF 
GO
ALTER DATABASE [QueryTest] SET AUTO_CLOSE OFF 
GO
ALTER DATABASE [QueryTest] SET AUTO_SHRINK OFF 
GO
ALTER DATABASE [QueryTest] SET AUTO_UPDATE_STATISTICS ON 
GO
ALTER DATABASE [QueryTest] SET CURSOR_CLOSE_ON_COMMIT OFF 
GO
ALTER DATABASE [QueryTest] SET CURSOR_DEFAULT  GLOBAL 
GO
ALTER DATABASE [QueryTest] SET CONCAT_NULL_YIELDS_NULL OFF 
GO
ALTER DATABASE [QueryTest] SET NUMERIC_ROUNDABORT OFF 
GO
ALTER DATABASE [QueryTest] SET QUOTED_IDENTIFIER OFF 
GO
ALTER DATABASE [QueryTest] SET RECURSIVE_TRIGGERS OFF 
GO
ALTER DATABASE [QueryTest] SET  DISABLE_BROKER 
GO
ALTER DATABASE [QueryTest] SET AUTO_UPDATE_STATISTICS_ASYNC OFF 
GO
ALTER DATABASE [QueryTest] SET DATE_CORRELATION_OPTIMIZATION OFF 
GO
ALTER DATABASE [QueryTest] SET TRUSTWORTHY OFF 
GO
ALTER DATABASE [QueryTest] SET ALLOW_SNAPSHOT_ISOLATION OFF 
GO
ALTER DATABASE [QueryTest] SET PARAMETERIZATION SIMPLE 
GO
ALTER DATABASE [QueryTest] SET READ_COMMITTED_SNAPSHOT OFF 
GO
ALTER DATABASE [QueryTest] SET HONOR_BROKER_PRIORITY OFF 
GO
ALTER DATABASE [QueryTest] SET RECOVERY FULL 
GO
ALTER DATABASE [QueryTest] SET  MULTI_USER 
GO
ALTER DATABASE [QueryTest] SET PAGE_VERIFY CHECKSUM  
GO
ALTER DATABASE [QueryTest] SET DB_CHAINING OFF 
GO
ALTER DATABASE [QueryTest] SET FILESTREAM( NON_TRANSACTED_ACCESS = OFF ) 
GO
ALTER DATABASE [QueryTest] SET TARGET_RECOVERY_TIME = 60 SECONDS 
GO
ALTER DATABASE [QueryTest] SET DELAYED_DURABILITY = DISABLED 
GO
EXEC sys.sp_db_vardecimal_storage_format N'QueryTest', N'ON'
GO
ALTER DATABASE [QueryTest] SET QUERY_STORE = OFF
GO
USE [QueryTest]
GO
/****** Object:  Table [dbo].[Table1]    Script Date: 5/18/2021 3:37:20 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Table1](
	[Table1Key] [int] NOT NULL,
	[Date] [datetime] NOT NULL,
	[Table2Key] [int] NOT NULL,
	[Table3Key] [int] NOT NULL,
	[ProjectTableKey] [int] NOT NULL,
	[Data] [int] NOT NULL,
 CONSTRAINT [PK_Table1] PRIMARY KEY CLUSTERED 
(
	[Table1Key] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
/****** Object:  Table [dbo].[Table2]    Script Date: 5/18/2021 3:37:20 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Table2](
	[Table2Key] [int] NOT NULL,
	[ProjectPhaseKey] [int] NULL,
 CONSTRAINT [PK_Table2] PRIMARY KEY CLUSTERED 
(
	[Table2Key] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
ALTER TABLE [dbo].[Table1]  WITH CHECK ADD  CONSTRAINT [FK_Table1_Table2] FOREIGN KEY([Table2Key])
REFERENCES [dbo].[Table2] ([Table2Key])
GO
ALTER TABLE [dbo].[Table1] CHECK CONSTRAINT [FK_Table1_Table2]
GO
USE [master]
GO
ALTER DATABASE [QueryTest] SET  READ_WRITE 
GO