Yes, Join is a powerful tool.
In case you already have created a table a lot of multiples there are several ways to identify and delete duplicate.
Below is my (current) favorite jsl snippet for deleting multiple instances. It now compares all columns, but can be tweaked to just consider a limited set of columns.
// Keep only first instance of multiples
dt = Current Data Table(); // Table with potential multiples
instance = Parse("ColMin(Row(), :Name(\!"" || Concat Items(dt << get column names(string), "\!"), :Name(\!"") || "\!"))");
dt << delete rows(dt<<get rows where(instance < Row()));