Connecting-To: Using parameters

Mon, 01 Jan 0001 00:00:00 +0000

You can use parameters to execute similar SQL statements repeatedly and efficiently.

Using parameters

VerticaParameters are an extension of the System.Data.DbParameter base class in ADO.NET and are used to set parameters in commands sent to the server. Use Parameters in all queries (SELECT/INSERT/UPDATE/DELETE) for which the values in the WHERE clause are not static; that is for all queries that have a known set of columns, but whose filter criteria is set dynamically by an application or end user. Using parameters in this way greatly decreases the chances of a SQL injection issue that can occur when simply creating a SQL query from a number of variables.

Parameters require that a valid DbType, VerticaDbType, or System type be assigned to the parameter. See Data types and ADO.NET data types for a mapping of System, OpenText™ Analytics Database, and DbTypes.

To create a parameter placeholder, place either the at sign (@) or a colon (:) character in front of the parameter name in the actual query string. Do not insert any spaces between the placeholder indicator (@ or :) and the placeholder.

Note

The @ character is the preferred way to identify parameters. The colon (:) character is supported for backward compatibility.

For example, the following typical query uses the string 'MA' as a filter.

SELECT customer_name, customer_address, customer_city, customer_state
FROM customer_dimension WHERE customer_state = 'MA';

Instead, the query can be written to use a parameter. In the following example, the string MA is replaced by the parameter placeholder @STATE.

SELECT customer_name, customer_address, customer_city, customer_state
FROM customer_dimension WHERE customer_state = @STATE;

For example, the ADO.net code for the prior example would be written as:

VerticaCommand command = _conn.CreateCommand();
command.CommandText = “SELECT customer_name, customer_address, customer_city, customer_state
    FROM customer_dimension WHERE customer_state = @STATE”;
command.Parameters.Add(new VerticaParameter( “STATE”, VerticaType.VarChar));
command.Parameters["STATE"].Value = "MA";

Note

Although the VerticaCommand class supports a Prepare() method, you do not need to call the Prepare() method for parameterized statements because the database automatically prepares the statement for you.

Connecting-To: Creating and rolling back transactions

Mon, 01 Jan 0001 00:00:00 +0000

Creating transactions

Transactions in OpenText™ Analytics Database are atomic, consistent, isolated, and durable. When you connect to a database using the ADO.NET Driver, the connection is in autocommit mode and each individual query is committed upon execution. You can collect multiple statements into a single transaction and commit them at the same time by using a transaction. You can also choose to rollback a transaction before it is committed if your code determines that a transaction should not commit.

Transactions use the VerticaTransaction object, which is an implementation of DbTransaction. You must associate the transaction with the VerticaCommand object.

The following code uses an explicit transaction to insert one row each into to tables of the VMart schema.

To create a transaction in OpenText™ Analytics Database using the ADO.NET driver:

Create a connection to the database.

Create a command object using the connection.

VerticaCommand command = _conn.CreateCommand();

Start an explicit transaction, and associate the command with it.

VerticaTransaction txn = _conn.BeginTransaction();
command.Connection = _conn;
command.Transaction = txn;

Execute the individual SQL statements to add rows.

command.CommandText =
     "insert into product_dimension values( ... )";
command.ExecuteNonQuery();
command.CommandText =
     "insert into store_orders_fact values( ... )";

Commit the transaction.
```
txn.Commit();
```

Rolling back transactions

If your code checks for errors, then you can catch the error and rollback the entire transaction.

VerticaTransaction txn = _conn.BeginTransaction();
VerticaCommand command = new
        VerticaCommand("insert into product_dimension values( 838929, 5, 'New item 5' )", _conn);
// execute the insert
command.ExecuteNonQuery();
command.CommandText = "insert into product_dimension values( 838929, 6, 'New item 6' )";
// try insert and catch any errors
bool error = false;
try
{
    command.ExecuteNonQuery();
}
catch (Exception e)
{
    Console.WriteLine(e.Message);
    error = true;
}
if (error)
{
    txn.Rollback();
    Console.WriteLine("Errors. Rolling Back.");
}
else
{
    txn.Commit();
    Console.WriteLine("Queries Successful. Committing.");
}

Commit and rollback example

This example details how you can commit or rollback queries during a transaction.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using Vertica.Data.VerticaClient;
namespace ConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            VerticaConnectionStringBuilder builder = new VerticaConnectionStringBuilder();
            builder.Host = "192.168.1.10";
            builder.Database = "VMart";
            builder.User = "dbadmin";
            VerticaConnection _conn = new VerticaConnection(builder.ToString());
            _conn.Open();
            bool error = false;
                VerticaCommand command = _conn.CreateCommand();
                VerticaCommand command2 = _conn.CreateCommand();
                VerticaTransaction txn = _conn.BeginTransaction();
                command.Connection = _conn;
                command.Transaction = txn;
                command.CommandText =
                "insert into test values(1, 'test', 'test', 'test' )";
                Console.WriteLine(command.CommandText);
                try
                {
                    command.ExecuteNonQuery();
                }
                catch (Exception e)
                {
                    Console.WriteLine(e.Message);
                    error = true;
                }
                command.CommandText =
                "insert into test values(2, 'ear', 'eye', 'nose', 'extra' )";
                Console.WriteLine(command.CommandText);
                try
                {
                    command.ExecuteNonQuery();
                }
                catch (Exception e)
                {
                    Console.WriteLine(e.Message);
                    error = true;
                }
                if (error)
                {
                    txn.Rollback();
                    Console.WriteLine("Errors. Rolling Back.");
                }
                else
                {
                    txn.Commit();
                    Console.WriteLine("Queries Successful. Committing.");
                }
            _conn.Close();
        }
    }
}

The example displays the following output on the console:

insert into test values(1, 'test', 'test', 'test' )
insert into test values(2, 'ear', 'eye', 'nose', 'extra' )
[42601]ERROR: INSERT has more expressions than target columns
Errors. Rolling Back.

OpenText Analytics Database 26.2.x – Inserting data (ADO.NET)

Connecting-To: Using parameters

Using parameters

Note

Note

Connecting-To: Creating and rolling back transactions

Creating transactions

To create a transaction in OpenText™ Analytics Database using the ADO.NET driver:

Rolling back transactions

Commit and rollback example

See also