Doctrine table class inheritance when one subclass has no extra attributes

You are using joined inheritance model (class table inheritance), which uses a separate table for parent and each child. If you don't specify any fields in the child class, Doctrine will just create a table only containing ID field.

And a parent class can only use one type of inheritance, either class table inheritance or single table inheritance.

In that case, if you don't want to have a table with only id column in it, you need to change your data model.

Maybe this can help or add something new. It is not a how to answer but simply taking about concepts.

If you think on classes and you understand your model as: AbstractAction, FooAction and BarAction it is probably because you can have the same methods implemented in a different way on the subclasses or extending some parent method.

If you choose to represent these classes with tables and you choose the "all in one table with a discriminator attribute" i think you have no problem. For the BarAction you will have register with discriminator="BarAction" which will be reprsented by a BarAction.php entity class.

On the other hand if you opt for using different table I consider you need one table per "class". The table for BarAction will only containd the ID field for the AbstractAction but its is required to "classify" (or discriminate) your data as a FooAction.

In summary, I think three tables representing three classes are a fine solution, although the BarAction table simply contains a "link" to the parent table.