Unexpected NULL rows and sort direction loss when sorting FilamentPHP table columns by relationship attributes

Answer

With Filament 3.2+ and a column defined as $table->column('user.name', 'User Name')->sortable(), Filament adds the join for you. You do not need to manually join the relationship for sorting to work.

Sort direction is stored in the URL as ?sort=user.name&sort_direction=asc|desc for any sortable column, including relationship columns. It persists after a page reload as long as the column definition is unchanged and the table query is not overridden in a way that removes the join.

Confirmed facts

• In Filament 3.2+, calling ->sortable() on a dot-notation column causes Filament to add a LEFT JOIN to the related table automatically.
• The join type used by Filament for sorting is LEFT JOIN, so rows with a NULL foreign key are retained in the result set.

Likely explanation for the symptoms you see

• NULL row placement is database dependent. With a LEFT JOIN the related attribute is NULL when the foreign key is NULL. MySQL treats NULL as lowest, so ASC puts NULL rows first and DESC puts them last. Other databases may order NULLs differently.
• If you use modifyQueryUsing() or add constraints that change the join to INNER JOIN, rows with NULL foreign keys are filtered out and the apparent sort direction can seem lost.
• URL persistence can appear broken if the column key changes, the query is rebuilt without the sortable state, or a custom query removes the join that Filament added.

Steps to verify for this case

1. Confirm the join is present. Enable query listening temporarily and load the table with the relationship column sorted.

DB::listen(function ($query) { logger()->info($query->sql, $query->bindings); });

Look for a LEFT JOIN on the related table when sort=user.name is in the request.

2. Check URL persistence. Click the column header to sort ASC then DESC, reload the page, and verify sort and sort_direction remain in the URL and the order is unchanged.
3. Test NULL handling. Insert test rows with null and non-null foreign keys and observe order in both ASC and DESC. If you need explicit control, set null ordering on the column:

$table->column('user.name')->sortable()->nullsLast();

Use nullsFirst() or nullsLast() to make placement deterministic across databases.

One diagnostic detail that changes the recommendation: which database engine you are using and whether modifyQueryUsing() is applied to the table query. NULL ordering defaults differ by DB, and a custom query can replace Filament’s LEFT JOIN.