Retrieves only one row from the result. Returns null when no row matches, the model when exactly one row matches, and throws a PostgrestException (status 406) when more than one row matches. Constrain the query (for example, filter on a primary key or unique column) so it can only match a single row.
var result = await supabase.From<City>()
.Select(x => new object[] { x.Name, x.CountryId })
.Single();