QGIS joins 2 FIELDS

The key here is to make two fields into one. Like lot and plan becomes lotplan (eg. Lot 10 on SP1234 -> 10/SP1234) in BOTH tables.. then join as normal. This is easy in Excel by adding a new header cell and use the function =A1 & "\" & B1 (or whatever you cells are) and then use field calc in QGIS. – Michael Miles-Stimson

So... this is how I have done it. For large number of entries, it works. I created drop-down menus in excel , then concatenate in excel: concatenate(a1;b1) then concatenate same fields in the shapefile using FIELD CALCULATOR : concat(field1,field2)

Then Join both and that.s it.

For few registries, I think you can enter data manually on a new column (shapefile). Many thanks for the idea, Elsa