Editing Data source name

{{Short description|String that has an associated data structure used to describe a connection to a data source}}
{{More citations needed|date=April 2022}}

[[Internet|In]] [[computing]], a '''data source name''' ('''DSN''', sometimes known as a '''database source name''', though "[[Computer file|data sources]]" can comprise other repositories apart from [[database management system|databases]]) is a string that has an associated [[data structure]] used to describe a connection to a data source. Most commonly used in connection with [[ODBC]], DSNs also exist for [[JDBC]] and for other data access mechanisms.  The term often overlaps with "[[connection string]]".  Most systems do not make a distinction between DSNs or connection strings and the term can often be used interchangeably.<ref>[https://www.gridgain.com/docs/latest/developers-guide/SQL/ODBC/connection-string-dsn Connection String and DSN]</ref>

DSN attributes may include, but are not limited to:<ref>[https://docs.microsoft.com/en-us/sql/connect/odbc/dsn-connection-string-attribute?view=sql-server-ver15 ODBC DSN connection strings]</ref>

* the name of the data source
* the location of the data source
* the name of a [[database driver]] which can access the data source
* a [[User identifier|user ID]] for data access (if required)
* a user password for data access (if required)

The system administrator of a client machine generally creates a separate DSN for each relevant data source.

Standardizing DSNs offers a level of [[indirection]]; various applications (for example: [[Apache HTTP Server|Apache]]/[[PHP]] and [[Internet Information Services|IIS]]/[[Active Server Pages|ASP]]) can take advantage of this in accessing shared data sources.

== Types of data source name ==
Two kinds of DSN exist:

* '''Machine DSNs''' – stored in collective configuration files (e.g., {{code|/etc/odbc.ini}}, {{code|~/.odbc.ini}}) and/or system resources (e.g., Windows Registry {{code|HKLM\Software\ODBC\odbc.ini}})
* '''File DSNs''' – stored in the filesystem with one DSN per file

These are further broken down into
* '''System DSNs''' – accessible by any and all processes and users of the system, stored in a centralized location (e.g., {{code|/etc/odbc.ini}}, {{code|/etc/odbc_file_dsns/<filename>}})
* '''User DSNs''' – accessible only by the user who created the DSN, stored in a user-specific location (e.g., {{code|~/.odbc.ini}}, {{code|~/odbc_file_dsns/<filename>}})

== Example of use ==
Software (e.g., Crystal Reports, Microsoft Excel, PHP, Perl, Python, Ruby) users can submit CRUD (Create, Read, Update, Delete) queries to a data source by establishing a connection to the DSN.

ASP ([[VBScript]]) code to open a DSN connection might look like the following:

<syntaxhighlight lang="vbscript">
Dim DatabaseObject1
Set DatabaseObject1 = Server.CreateObject("ADODB.Connection")
DatabaseObject1.Open("DSN=example;")
</syntaxhighlight>

In [[PHP]] using the [https://pear.php.net/package/DB/ PEAR::DB] package to open a connection without an external DSN (a "DSN-less connection", i.e., using a Connection String){{Clarify|How is this an example of DSN use|date=June 2013}}, the code might resemble the following:

<syntaxhighlight lang="php">
require_once("DB.php");
//$dsn = "<driver>://<username>:<password>@<host>:<port>/<database>";
$dsn = "mysql://john:pass@localhost:3306/my_db";
$db = DB::connect($dsn);
</syntaxhighlight>

PHP with PDO:<ref>{{cite web |title=PHP: PDO - Manual |url=https://www.php.net/pdo |website=www.php.net |access-date=22 January 2025 |language=en}}</ref>
<syntaxhighlight lang="php">
$dsn = "mysql:host=localhost;dbname=example";
$dbh = new PDO($dsn, $username, $password);
</syntaxhighlight>

In [[Perl]], using the [[Perl DBI]] module, each driver has its own syntax for the DSN attributes. The only requirement that DBI makes is that all the information, except for username and password is supplied in a single string argument.

<syntaxhighlight lang="perl">
my $dsn = "DBI:Pg:database=finance;host=db.example.com;port=$port";
   $dsn = "DBI:mysql:database=$database;host=$hostname;port=$port";
   $dsn = "DBI:Oracle:host=$host;sid=$sid;port=$port";
   $dsn = "DBI:SQLite:dbname=$dbfilename";

my $dbh = DBI->connect($dsn,'username','password');
</syntaxhighlight>

== See also ==
* [[Datasource]]
* [[ADO.NET]]
* [[JDBC]]
* [[ODBC]]
* [[OLE DB]]

== References ==
<references/>

{{Database}}

[[Category:Data access technologies| ]]