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About Connection Strings

A connection string is a string version of the initialization properties needed to connect to a database and enables you to easily store connection information or to pass it between applications. Without a connection string, you would be required to store or pass a complex array of structures to access data. When accessing OLE DB the connection string is passed as a parameter to create an OLE DB data source object.

In some cases, rather than using the standard data link user interface, it might be desirable to build a connection string within an application—for example, if you want to fine-tune the database connection properties. In these cases, it is important that the connection string syntax adhere to the formatting rules described in the following sections.

Basic Connection String Format

The basic format of a connection string is based on the ODBC connection string. The string consists of a series of keyword/value pairs separated by semicolons. The equal sign (=) connects each keyword and its value.

Example:   keyword1=value; keyword2=value

The Provider Keyword

The Provider keyword identifies the OLE DB provider to be used. To specify your OLE DB provider, set the value of the Provider keyword to the VersionIndependentProgID value of the provider.

Example:   Provider=MSDASQL

The value can also be set to the ProgID of the provider, which may have a version attached to it.

Example:   Provider=MSDASQL.1

If two versions of a provider are installed on the same system, use the ProgID to specify exactly which version to use. If two versions are installed on a system and the VersionIndependentProgID value is specified, the most recent version of the provider is used.

If no Provider keyword is in the string, the OLE DB Provider for ODBC (MSDASQL) is the default value. This provides backward compatibility with ODBC connection strings. The ODBC connection string in the following example can be passed in, and it will successfully connect.

Example:   Driver={SQL Server};Server=MyServer;db=pubs;uid=sa;pwd=MyPassword

If the Provider keyword is specified but names a provider that does not exist or is invalid, as in the following example, an error is returned.

Example:   Provider=;Database=MyDatabase

Specifying a Keyword

To identify a keyword used after the Provider keyword, use the property description of the OLE DB initialization property that you want to set. For example, the property description of the standard OLE DB initialization property DBPROP_INIT_LOCATION is Location. Therefore, to include this property in a connection string, use the keyword Location.

Example:   Provider=MSDASQL;Location=Pubs

Note   Standard OLE DB properties are documented under the OLE DB Initialization property group (DBPROPSET_DBINIT) in Appendix C: OLE DB Properties. For information about provider-specific initialization properties, see the documentation that came with your provider.

Keywords can contain any printable character except for the equal sign (=). All of the following examples are correct.

Example:   Jet OLE DB:System Database=c:\system.mda

The keyword is "Jet OLE DB:System Database".

Example:   Authentication;Info=Column 5

The keyword is "Authentication;Info".

If a keyword contains an equal sign (=), it must be preceded by an additional equal sign to indicate that it is part of the keyword.

Example:   Verification==Security=True

The keyword is "Verification=Security".

If multiple equal signs appear, each one must be preceded by an additional equal sign.

Example:   Many====One=Valid

The keyword is "Many==One".

Example:   TooMany===False

The keyword is "TooMany=".

 


Related Topics:

Connection properties

About database connections

Connect to existing database

Object Browser elements

Open Microsoft Access files with the program

Create a shortcut to a database on the Shortcut Bar

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