Formatting Rules for Connection Strings Print

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Formatting Rules for Connection Strings

As a string, there are no built in checks or constraints on how to format the connection string. This article walks through the basic rules for creating a connection string that will work.


This is general rules adopted by most drivers and providers. However, keep in mind that these rules is not 100% accurate for every driver and every situation. Never the less, following and knowing about these basic rules will keep some common problems out of the way.

The rules

All blank characters, except those placed within a value or within quotation marks, are ignored

Blank characters will though affect connection pooling mechanism, pooled connections must have the EXACT same connection string

If a semicolon (;) is part of a value it must be delimited by quotation marks (")

Use a single-quote (') if the value begins with a double-quote (")

Conversely, use the double quote (") if the value begins with a single quote (')

No escape sequences are supported

The value type is NOT relevant

Names are not case sensitive

If a KEYWORD=VALUE pair occurs more than once in the connection string, the value associated with the LAST occurrence is used

But!... if the PROVIDER keyword occurs multiple times in the string, the FIRST occurrence is used.

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.


Knowing about these basic rules will keep hard to track errors away from you. Take some time understanding these rules and a couple of minutes choosing what parameters to specify when connecting your application to the data source.

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