A discriminator value is the literal marker Hibernate uses to identify an entity subtype when an inheritance hierarchy shares one table. The value is stored in an internal discriminator column, not as an entity property; for example, `CC` identifies `CreditCard` rows. section 7.3
Explicit subtype mapping
With `@DiscriminatorColumn(name = "BD_TYPE")` on `BillingDetails`, annotate a concrete subtype as `@DiscriminatorValue("CC")`. Hibernate writes `CC` to `BD_TYPE` and uses `where BD_TYPE='CC'` when querying `CreditCard` entities. Explicit values avoid provider-dependent defaults. section 7.3
