Cannot resolve joined field due to ambiguous joins

I have a model which has transactions, and two of the columns join to the same table (employee) --- Salesrep and ProjectManager.

I then have a seperate model which uses the first model as its starting data.
However, in this second model I am getting the following error:

Cannot resolve joined field due to ambiguous joins: table dim_employee (ID 334) joined multiple times. You need to specify an explicit :join-alias in the field reference.

Where do I go to specify an explicit join alias?

Metabase has several existing issues when using multiple joins to the same table, doesn't seem to matter if your doing it with models or raw source tables, explicit joins in the builder or those modelled in the Metabase metadata, or some combination of these. They've got an issue here Duplicated columns in a source query cannot be distinguished · Issue #36185 · metabase/metabase · GitHub to cover most of them, go give it a thumbs up to hopefully get some movement.

I find that making the base model via SQL, and not setting up the metadata to link to other tables can help work around some of these issues, but you lose some of the good stuff for models.

I trip over this root issue quite a bit, even if the data is correct and it's just reflected in the names given to fields it gets confusing and pretty frustrating.

I´m getting the same problem

I've found that the best approach is to stick with a simple star schema. That way, you never need to define joins.
All my customers are limited to just using views rather than the 'real' tables. That way, I can simulate a proper star schema without going to all the effort of creating a data warehouse.
If you're joining by multiple fields between tables, create a single column by concatenating in a view.