Question at position 15 Management has requested that you build an employee database. You need to include each employee's current position and salary, as well as all prior positions and salaries with the company. You decide to use a one-to-many structure: an employee table with the main information such as name and address, and an employment table with position and salary history. You can use the employeeID field to connect them. What is employment.employeeID an example of? alternate key primary key secondary key foreign key

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BlackTom AI · Accepted Answer

Consider the scenario described: two related tables are used, an employee table and an employment (history) table, with a linking field employeeID that connects records across these tables.
Option: alternate key
This would be a candidate key that could serve as a key but is not the primary key. In this design, employeeID is being used to link two tables, not simply to serve as an alternate unique identifier within one table. So calling it an alternate key is not the best fit here.
Option: primary key
A primary key uniquely identifies each row within a single table. In the employment table, the primary key would typically be something like an employmentID (a unique history record). The employeeID in the employment table is used to reference the employee, not to uniquely identify each employment record. Therefore, it is not the primary key of the employment table.
Option: secondary key
A secondary key is a non-unique key used for data retrieval that is not the primary key. While employeeID could potentially be used for lookup, the core role of employeeID in the employment table is to establish a link to the employee table, not just to facilitate retrieval in a non-unique way. Thus labeling it as a secondary key is inaccurate for describing its main purpose here.
Option: foreign key
A foreign key is a field (or collection of fields) in one table that uniquely identifies a row of another table. It creates a referential link between the two tables. In this design, employment.employeeID connects to employee.employeeID, enabling the one-to-many relationship where one employee has many employment history records. This matches the standard definition of a foreign key and its role in relational databases.
In summary, the most accurate classification for employment.employeeID in this context is that it serves as a foreign key, establishing the relationship between the employee table and the employment history table. The other options describe alternative keys or retrieval aids but do not capture the linking function being used here.

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