BOL’s description of the JOIN() Function: “Returns a string created by joining a number of substrings contained in an array.”. The syntax of the function is as follows:

=JOIN(List [,delimiter])

List – Required. One-dimensional array containing substrings to be joined

Delimiter – Optional. String character used to separate substrings. If omitted, a space “ “ will be used.

So, the JOIN() Function concatenates an array’s values, using either a default space or the specified separator (for example, “, “) to separate the values.

What are the practical uses of this function as it relates to Reporting Services?

A common use of the function in Reporting Services is to display the values being used in a Multi-valued Parameter. You may for example have a report that has a parameter that filters Sales Regions. A requirement of the report is to display, in the header, the Sales Regions that the report is for. In the header of the report you would include the following expression:

=”Monthly Sales Report, for Regions:  ” & JOIN(Parameters!SalesRegion.Value, “, “)

Previewing this in the report with the following regions selected from the SalesRegion Multi-Value Parameter:

• North America
• South America
• Southern Africa

Will result in the following Header string:

Monthly Sales Report, for Regions:   North America, South America, Southern Africa

I have mentioned this function here as I find it very useful and have used it on many occasions. The above use is only one of many, but for me, is the most common.