Answer by James Whiteside for Polymorphism in databases

To expand on the reference to NoSQL solutions in Cristophe's answer, a polymorphic database is perfect for this kind of use case. This would allow you to natively implement the polymorphic data model without an ORM or integrity managament.

I've put together a quick TypeDB schema that should work for your sample data:

defineplayer sub entity,    abstract,    owns name @key;attack-player sub player,    owns strength,    owns constitution;defense-player sub player,    owns health,    owns resistance;support-player sub player,    owns mana,    owns willpower;name sub attribute, value string;skill sub attribute, abstract, value long;strength sub skill;constitution sub skill;health sub skill;resistance sub skill;mana sub skill;willpower sub skill;

Here I've defined an entity hierarchy, with each of the player roles attack-player, defense-player, and support-player extending an abstract player supertype. I've also defined an attribute hierarchy, so all of the skills extend an abstract skill supertype. Each player role owns different skills as needed, and they all inherit name from player.

Using this schema, your sample data can be inserted as follows:

insert$player-1 isa attack-player,    has name "name1",    has strength 10,    has constitution 5;$player-2 isa attack-player,    has name "name2",    has strength 7,    has constitution 7;$player-3 isa defense-player,    has name "name3",    has health 8,    has resistance 8;$player-4 isa defense-player,    has name "name4",    has health 10,    has resistance 10;$player-5 isa support-player,    has name "name5",    has mana 4,    has willpower 3;

Now your data can be queried polymorphically. To get the attack skill of "name1", you can use:

match$player isa player,    has name "name1",    has attack $atk;get $atk;

To get all the skills of "name1", use:

match$player isa player,    has name "name1",    has skill $skl;get $skl;

To get defense players and their skills, use:

match$player isa defense-player,    has name $name,    has health $hlt,    has resistance $res;get $name, $hlt, $res;

To get all players that have a mana skill regardless of their player role, use:

match$player isa player,    has name $name,    has mana $mna;get $name, $mna;

To get all players and all of their skills, use:

match$player isa player,    has name $name,    has skill $skl;get $name, $skl;

Disclaimer: I have worked on TypeDB.