Study Entity-Relationship Modeling — complete the practice problems in your notebook.
In an ER diagram, a weak entity is one that:
A weak entity depends on a strong entity for its identity — it has no primary key of its own (only a partial key).
Weakness is about key dependency, not attribute count.
A weak entity uses a double rectangle. The double diamond is the identifying relationship connecting it to its owner.
A many-to-many relationship between Students and Courses is typically resolved in a relational schema by:
A single FK from Students to Courses would allow each student only one course (one-to-many). M:N requires a junction table.
Storing lists in a single column violates 1NF. Always use a junction table for M:N.
Duplication causes update anomalies: changing a student's name would require updating many rows.