How are super- and subtype relationships in ER diagrams represented as tables?

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I am learning how to interpret Entity Relationship Diagrams into SQL DDL statements and I am confused by differences in notation. Consider a disjoint relationship as in the following diagram:

"Vehicle" box connects to "IsA" triangle, noted as "disjoint," which connects separately to "2WD" box and "4WD" box.

Would this be represented as:

  1. Vehicle, 2WD and 4WD tables (2WD and 4WD would point to the PK of Vehicle); or
  2. ONLY the 2WD and 4WD tables (and NO Vehicle table), both of which would duplicate whatever attributes Vehicle would have had?

I think these are other ways of writing the relationship:

"Vehicle" box connects with a thick line to "IsA" triangle, which connects with thin lines separately to "2WD" box and "4WD" box. "Vehicle" box connects to "IsA" triangle, which connects separately to "2WD" box and "4WD" box, all by thin lines.

I'm looking for a clear explanation of the difference in regard to what tables you'd end up with for each diagram.

entity-relationship erd database-design database
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