Following are the definitions of 2 tables in a DBMS:

EMPLOYEE(EmpID,FirstName,LastName,PositionID,Salary)

POSITION(PositionID,PositionName,DeptID,EmplID)

What is the foreign key in the Table EMPLOYEE?

Question

Following are the definitions of 2 tables in a DBMS:

EMPLOYEE(EmpID,FirstName,LastName,PositionID,Salary)

POSITION(PositionID,PositionName,DeptID,EmplID)

What is the foreign key in the Table EMPLOYEE?

BlackTom AI · Accepted Answer

PositionID in EMPLOYEE is a foreign key because it references the primary key of the POSITION table.

1) Relevant concepts:
- Primary key: a column (or set) that uniquely identifies rows in its own table (e.g., PositionID in POSITION or EmpID in EMPLOYEE).
- Foreign key: a column in one table whose values must match values of a primary (or candidate) key in another table, enforcing referential integrity between related rows.

2) Step-by-step reasoning:
- EMPLOYEE has attributes: EmpID, FirstName, LastName, PositionID, Salary.
- POSITION has attributes: PositionID, PositionName, DeptID, EmplID.
- The shared attribute name PositionID appears in both tables. In POSITION it is the natural candidate for the primary key (it uniquely identifies a position).
- A typical relationship is that each employee holds a position; therefore EMPLOYEE.PositionID stores the identifier of the position that the employee occupies.
- By definition, the column in EMPLOYEE that stores identifiers from the POSITION table is a foreign key pointing to POSITION.PositionID.

3) Intermediate mapping steps (no numeric calculation needed):
- Identify candidate key in POSITION: PositionID → uniquely identifies rows in POSITION.
- Identify referencing column in EMPLOYEE: PositionID → stores values that should match POSITION.PositionID.
- Therefore EMPLOYEE.PositionID → FOREIGN KEY referencing POSITION(PositionID).

4) Why the correct answer is correct:
- EMPLOYEE.PositionID enforces the relationship to POSITION by containing position identifiers that must exist in the POSITION table. That exactly matches the foreign key definition.

5) Why other options are incorrect:
- EmpID: this is the likely primary key of EMPLOYEE, not a foreign key.
- FirstName / LastName: these are descriptive attributes, not keys referencing another table.
- none of the options listed: incorrect because PositionID is present and serves as the foreign key.

6) Conclusion:
Thus the foreign key in the EMPLOYEE table is PositionID, which matches the provided answer: PositionID.

Following are the definitions of 2 tables in a DBMS: EMPLOYEE(EmpID,FirstName,LastName,PositionID,Salary) POSITION(PositionID,PositionName,DeptID,EmplID) What is the foreign key in the Table EMPLOYEE?单项选择题

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