Return list of Students by ZipCode Count

April 28, 2022

I am trying to get a list of students that live in the same zip code where zip code count > 1.

I tried the following and get nothing in my query. If I remove s.Student, I get results of zipcode and count, but I want to include student also.

SELECT s.Student, z.ZipCode, COUNT(s.ZipCodeId) As 'Zip Code Count'
FROM Students s
INNER JOIN ZipCodes z ON z.ZipCodeId = s.ZipCodeId
GROUP BY s.Student, z.ZipCode
HAVING COUNT(z.ZipCode) > 1

Below is the database script of the database and its corresponding tables I am using.

USE [master]
GO
/****** Object:  Database [School]    Script Date: 4/26/2022 7:44:58 PM ******/
CREATE DATABASE [School]
 CONTAINMENT = NONE
 ON  PRIMARY 
( NAME = N'School', FILENAME = N'C:\Users\mylaptop\School.mdf' , SIZE = 8192KB , MAXSIZE = UNLIMITED, FILEGROWTH = 65536KB )
 LOG ON 
( NAME = N'School_log', FILENAME = N'C:\Users\mylaptop\School_log.ldf' , SIZE = 8192KB , MAXSIZE = 2048GB , FILEGROWTH = 65536KB )
GO
ALTER DATABASE [School] SET COMPATIBILITY_LEVEL = 130
GO
IF (1 = FULLTEXTSERVICEPROPERTY('IsFullTextInstalled'))
begin
EXEC [School].[dbo].[sp_fulltext_database] @action = 'enable'
end
GO
ALTER DATABASE [School] SET ANSI_NULL_DEFAULT OFF 
GO
ALTER DATABASE [School] SET ANSI_NULLS OFF 
GO
ALTER DATABASE [School] SET ANSI_PADDING OFF 
GO
ALTER DATABASE [School] SET ANSI_WARNINGS OFF 
GO
ALTER DATABASE [School] SET ARITHABORT OFF 
GO
ALTER DATABASE [School] SET AUTO_CLOSE OFF 
GO
ALTER DATABASE [School] SET AUTO_SHRINK OFF 
GO
ALTER DATABASE [School] SET AUTO_UPDATE_STATISTICS ON 
GO
ALTER DATABASE [School] SET CURSOR_CLOSE_ON_COMMIT OFF 
GO
ALTER DATABASE [School] SET CURSOR_DEFAULT  GLOBAL 
GO
ALTER DATABASE [School] SET CONCAT_NULL_YIELDS_NULL OFF 
GO
ALTER DATABASE [School] SET NUMERIC_ROUNDABORT OFF 
GO
ALTER DATABASE [School] SET QUOTED_IDENTIFIER OFF 
GO
ALTER DATABASE [School] SET RECURSIVE_TRIGGERS OFF 
GO
ALTER DATABASE [School] SET  DISABLE_BROKER 
GO
ALTER DATABASE [School] SET AUTO_UPDATE_STATISTICS_ASYNC OFF 
GO
ALTER DATABASE [School] SET DATE_CORRELATION_OPTIMIZATION OFF 
GO
ALTER DATABASE [School] SET TRUSTWORTHY OFF 
GO
ALTER DATABASE [School] SET ALLOW_SNAPSHOT_ISOLATION OFF 
GO
ALTER DATABASE [School] SET PARAMETERIZATION SIMPLE 
GO
ALTER DATABASE [School] SET READ_COMMITTED_SNAPSHOT OFF 
GO
ALTER DATABASE [School] SET HONOR_BROKER_PRIORITY OFF 
GO
ALTER DATABASE [School] SET RECOVERY SIMPLE 
GO
ALTER DATABASE [School] SET  MULTI_USER 
GO
ALTER DATABASE [School] SET PAGE_VERIFY CHECKSUM  
GO
ALTER DATABASE [School] SET DB_CHAINING OFF 
GO
ALTER DATABASE [School] SET FILESTREAM( NON_TRANSACTED_ACCESS = OFF ) 
GO
ALTER DATABASE [School] SET TARGET_RECOVERY_TIME = 60 SECONDS 
GO
ALTER DATABASE [School] SET DELAYED_DURABILITY = DISABLED 
GO
ALTER DATABASE [School] SET QUERY_STORE = OFF
GO
USE [School]
GO
ALTER DATABASE SCOPED CONFIGURATION SET LEGACY_CARDINALITY_ESTIMATION = OFF;
GO
ALTER DATABASE SCOPED CONFIGURATION SET MAXDOP = 0;
GO
ALTER DATABASE SCOPED CONFIGURATION SET PARAMETER_SNIFFING = ON;
GO
ALTER DATABASE SCOPED CONFIGURATION SET QUERY_OPTIMIZER_HOTFIXES = OFF;
GO
USE [School]
GO
/****** Object:  Table [dbo].[Instructors]    Script Date: 4/26/2022 7:44:59 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Instructors](
    [InstructorId] [int] IDENTITY(1,1) NOT NULL,
    [Instructor] [varchar](50) NOT NULL,
    [ZipCodeId] [int] NOT NULL
) ON [PRIMARY]
GO
/****** Object:  Table [dbo].[Students]    Script Date: 4/26/2022 7:44:59 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Students](
    [StudentId] [int] IDENTITY(1,1) NOT NULL,
    [Student] [varchar](50) NOT NULL,
    [ZipCodeId] [int] NOT NULL
) ON [PRIMARY]
GO
/****** Object:  Table [dbo].[ZipCodes]    Script Date: 4/26/2022 7:44:59 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[ZipCodes](
    [ZipCodeId] [int] IDENTITY(1,1) NOT NULL,
    [ZipCode] [varchar](9) NULL,
    [City] [varchar](50) NULL,
    [State] [varchar](25) NULL
) ON [PRIMARY]
GO
USE [master]
GO
ALTER DATABASE [School] SET  READ_WRITE 
GO

>Solution :

I think you need to query the Zip Codes which are used more than once, then join the Students on along with the Zip Code details e.g.

SELECT S.Student, Z.ZipCode, Z1.Num AS "Zip Code Count"
FROM (
    SELECT COUNT(*) Num, ZipCodeId
    FROM Students S
    GROUP BY ZipCodeId
    HAVING COUNT(*) > 1
) Z1
INNER JOIN Students S on S.ZipCodeId = Z1.ZipCodeId
INNER JOIN ZipCodes Z on Z.ZipCodeId = Z1.ZipCodeId;

Note: You don’t use single quotes (') to delimit a column name – you use double quotes (") or square brackets ([]).

Also, sample data would allow testing of our solutions.