C# SqlCommand Example: SELECT TOP, ORDER BY

Use SqlCommand from System.Data.SqlClient. Specify SELECT TOP, ORDER BY statements.

SqlCommand. This type deals with databases. It executes SQL commands on a database. It sends an SQL command to a database that is specified by an SqlConnection object.

We then call instance methods to physically apply the command to the database. We use a SELECT TOP command text, and also ORDER BY.

Example. This program uses the SqlCommand data object in C#. We use SqlCommand in the context of a complete but trivial program that reads data from a specific database on the disk.

Info: The SqlCommand type has a public parameterized constructor and it can be used with one or more arguments.

And: The first parameter specifies the SQL statement. The second parameter is the SqlConnection. The third parameter is the SqlTransaction.

Important: This program interfaces with the SQL Server engine. It uses some project-specific external data.

SqlClient SqlDataReader

So: It will not work for you unless you change the connection string reference and the SQL command text for your environment.

C# program that uses SqlCommand instance using System; using System.Data.SqlClient; class Program { static void Main() { // // The program accesses the connection string. // ... It uses it on a connection. // string conString = ConsoleApplication1.Properties.Settings.Default.ConnectionString; using (SqlConnection connection = new SqlConnection(conString)) { connection.Open(); // // SqlCommand should be created inside using. // ... It receives the SQL statement. // ... It receives the connection object. // ... The SQL text works with a specific database. // using (SqlCommand command = new SqlCommand( "SELECT TOP 3 * FROM Dogs1 ORDER BY Weight", connection)) { // // Instance methods can be used on the SqlCommand. // ... These read data. // using (SqlDataReader reader = command.ExecuteReader()) { while (reader.Read()) { for (int i = 0; i < reader.FieldCount; i++) { Console.WriteLine(reader.GetValue(i)); } Console.WriteLine(); } } } } } } Output 7 Candy Yorkshire Terrier 25 Charles Cavalier King Charles Spaniel 57 Koko Shar Pei

Using. The SQL data objects are wrapped in a resource acquisition statement. This ensures that resources are properly acquired and disposed of when no longer needed.Using

Constructor. The call to the SqlCommand constructor uses 2 parameters. The first parameter is the actual SQL source text. This string uses SQL and is not compiled by the C# compiler.

And: The second parameter is the SqlConnection object. This is set up elsewhere in the program.

Overview: You must manually specify the connection to use on the SqlCommand. This can be done with a parameter on the constructor.

A summary. We wrote a complete program that reads from a database on the local disk. The SqlCommand has a constructor. You can specify its connection and the SQL text.

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C# SqlCommand Example: SELECT TOP, ORDER BY

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