In QGIS, I'm trying to input either 'Yes' or 'No' for a new field based upon the input of values of another 9 fields. I've attached a screenshot of what I'm trying to accomplish. Essentially if there is a 'Yes' in any of the 9 previous fields, then the new field will input 'Yes'. If however all 9 fields are NULL, then the new field will input 'No'.
You are looking for this function:
coalesce(NULL, 'Yes', NULL, 'No')
coalesce(NULL, NULL, NULL, 'No')
Returns the first non-NULL value from the expression list. This function can take any number of arguments.
So it will return the first non-NULL value it finds so if you make No the last value it will fallback to that value and report that.
coalesce("Field1", "Field2", "Field3", 'No')