[C#/COMMON/DAPPER] COUNT 집계 함수 사용하기

■ COUNT 집계 함수를 사용하는 방법을 보여준다.

▶ SQL Server 테이블 (SQL)


CREATE TABLE dbo.Student
(
    ID         INT          NOT NULL
   ,Name       NVARCHAR(50) NOT NULL
   ,CreateTime DATETIME     NOT NULL
    CONSTRAINT PKStudent PRIMARY KEY CLUSTERED
    (
	    ID 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

CREATE TABLE dbo.Student

(

ID INT NOT NULL

,Name NVARCHAR(50) NOT NULL

,CreateTime DATETIME NOT NULL

CONSTRAINT PKStudent PRIMARY KEY CLUSTERED

(

ID ASC

)

WITH

(

PAD_INDEX = OFF

,STATISTICS_NORECOMPUTE = OFF

,IGNORE_DUP_KEY = OFF

,ALLOW_ROW_LOCKS = ON

,ALLOW_PAGE_LOCKS = ON

) ON [PRIMARY]

▶ 예제 코드 (C#)


using System;
using System.Data.SqlClient;
using System.Linq;

using Dapper;

...

/// <summary>
/// 학생
/// </summary>
public class Student
{
    /// <summary>
    /// ID
    /// </summary>
    public int ID { get; set; }

    /// <summary>
    /// 성명
    /// </summary>
    public string Name { get; set; }

    /// <summary>
    /// 생성 일시
    /// </summary>
    public DateTime CreateTime { get; set; }
}

...

string connectionString = "Data Source=127.0.0.1;Initial Catalog=TestDB;UID=sa;PWD=1234;Timeout=30";

using(SqlConnection connection = new SqlConnection(connectionString))
{
    connection.Open();

    int? count = connection.Query<int?>("SELECT COUNT(*) FROM dbo.Student").First();

    Console.WriteLine(count);
}

using System;

using System.Data.SqlClient;

using System.Linq;

using Dapper;

...

/// <summary>

/// 학생

/// </summary>

public class Student

{

/// <summary>

/// ID

/// </summary>

public int ID { get; set; }

/// <summary>

/// 성명

/// </summary>

public string Name { get; set; }

/// <summary>

/// 생성 일시

/// </summary>

public DateTime CreateTime { get; set; }

}

...

string connectionString = "Data Source=127.0.0.1;Initial Catalog=TestDB;UID=sa;PWD=1234;Timeout=30";

using(SqlConnection connection = new SqlConnection(connectionString))

{

connection.Open();

int? count = connection.Query<int?>("SELECT COUNT(*) FROM dbo.Student").First();

Console.WriteLine(count);

}

※ 사용하는 조건문에 따라 조회 결과가 없을 수 있기 때문에 nullable을 사용했다.