How it works...

The last parameter for the LOOKUPVALUE, DIVIDE, FIND, and SEARCH functions is an optional parameter that specifies the value to return in the event that an error is generated by the function. In the case of the SELECTEDVALUE function, if there is no single value for the specified column, SELECTEDVALUE defaults to returning BLANK and so will never throw an error. This default return value can be overridden by specifying a second parameter for the SELECTEDVALUE function.

The internal error checking of the LOOKUPVALUE, DIVIDE, FIND, SEARCH, and SELECTEDVALUE functions is more efficient and therefore preferred over other methods of performing error checking in DAX, such as ISERROR, IFERROR, or HASONEVALUE.