Why isn't my database functoid working?

The database functoids Database Lookup and Value Extractor do not directly return error information; rather, they capture the information and supply it to the Error Return functoid for use by your map. You can use the Error Return functoid for error detection as in the following scenarios:

· When your map has a Database Lookup or Value Extractor functoid that is not behaving as expected. To see the error message, temporarily map the functoid to a field in the output schema.

· If your application expects different message content when database operations fail. You can use the Error Return functoid to detect an error and map the error message to an alternate structure so that downstream applications can react in a controlled manner.

To avoid errors that are detected only at run time, make sure that the parameter 1 to the Error Return functoid is the output of a Database Lookup functoid and not the output of any other functoid in the Database category.

Source: Microsoft