How to work with SQL Joins through ASP.Net C#

Default.aspx code <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

Default.aspx.cs code using System; using System.Configuration; using System.Data; using System.Linq; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.HtmlControls; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Xml.Linq; using System.Data.SqlClient; public partial class _Default : System.Web.UI.Page { string strConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString; string str; SqlCommand com; protected void Page_Load(object sender, EventArgs e) { SqlConnection con = new SqlConnection(strConnString); con.Open(); str = "SELECT a.empCode,a.date,a.[time] AS Intime,b.Outtime FROM employee A LEFT JOIN ( SELECT empCode,date,[time] AS Outtime FROM employee WHERE employee.inoutMode = 1 ) b ON a.empCode = b.empCode AND a.date = b.date WHERE a.inoutMode = 0"; com = new SqlCommand(str, con); SqlDataReader reader = com.ExecuteReader(); GridView1.DataSource = reader; GridView1.DataBind(); con.Close(); } }

Basically Joins are used to get values from multiple tables in one single table.... You will have to write Stored Procedures and pass parameters for the procedure and depending upon the parameter you have passed, you can join the tables and get your required values.

Passing a Unique ID of a table for joining is always good.

Check out this thread, where I have written a post for Join Query
http://www.c-sharpcorner.com/Forums/Thread/187890/how-to-join-three-tables-and-select-a-particular-field.aspx

Feel free to ask question if u have any doubt...

Cheers!!!