This tutorial shows in a simple Cω program how to use SQL Select to select data from the Customers table in the Northwind sample database provided with SQL Server 2000 and iterate over the results.
To run this tutorial, you may use the following project and source files:
These files are located in the \samples\SQL\Select subdirectory under the path where you installed Cω, which by default is C:\Program Files\Comega.
To run this sample, you need to have a SQL configuration file in the same directory as the Select.exe you make in Visual Studio. Here are the contents of the version of this file that Cω provided you as a starting point:
<configuration>
<appSettings>
<add key="Northwind" value="Data Source=(local);Initial Catalog=Northwind;Integrated Security=SSPI" />
</appSettings>
</configuration>
Verify that this is the correct SQL connection string for connecting to the
Northwind database on your SQL Server 2000 installation. If necessary, you can
modify the value attribute in the <add> element
When you have verified it is correct, press F5 in Visual Studio to make and run the sample.
The following is a complete Cω program that demonstrates how to use SQL Select to select data from the Customers table in the Northwind sample database provided with SQL Server 2000 and iterate over the results.
using System;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Northwind;
public class Test {
public static void Main( string[] args ) {
string mycity = args.Length>0 ? args[0] : "London";
Console.WriteLine("Contacts in \"{0}\"", mycity);
Console.WriteLine();
Console.WriteLine("CustomerID Contact");
Console.WriteLine("--------------------------------------------");
// Select expressions return a stream of rows. The type of each row
// is determined by the projection list.
struct{SqlString CustomerID; SqlString ContactName;}* res
= select CustomerID, ContactName
from DB.Customers
where City == mycity
order by ContactName;
// The foreach statement can infer the type of the iteration variable 'row'
// by looking at the strongly typed stream 'res.'
foreach( row in res ) {
Console.WriteLine("{0,-12} {1}", row.CustomerID, row.ContactName);
}
// You may also omit the type information on the left-hand side of an assignment
// statement, so there is no need to respecify a type that is already known.
res2 = select CustomerID, ContactName
from DB.Customers
where City == mycity
order by ContactName desc;
Console.WriteLine("\nIn reverse");
foreach( row in res2 ) {
Console.WriteLine("{0,-12} {1}", row.CustomerID, row.ContactName);
}
// Since its just an expression, you may also place the select expression directly
// inside the foreach statement.
Console.WriteLine("\nBy ID");
foreach( row in select CustomerID, ContactName
from DB.Customers
where City == mycity
order by CustomerID ) {
Console.WriteLine("{0,-12} {1}", row.CustomerID, row.ContactName);
}
Console.Write("\nPress ENTER to continue...");
Console.ReadLine();
}
}
Contacts in "London" CustomerID Contact -------------------------------------------- EASTC Ann Devon CONSH Elizabeth Brown SEVES Hari Kumar NORTS Simon Crowther AROUT Thomas Hardy BSBEV Victoria Ashworth In reverse BSBEV Victoria Ashworth AROUT Thomas Hardy NORTS Simon Crowther SEVES Hari Kumar CONSH Elizabeth Brown EASTC Ann Devon By ID AROUT Thomas Hardy BSBEV Victoria Ashworth CONSH Elizabeth Brown EASTC Ann Devon NORTS Simon Crowther SEVES Hari Kumar Press ENTER to continue...