Chapter 5: Problem 14

. Consider the following relations for a database that keeps track of business trips of salespersons in a sales office: SALESPERSON(SSN, Name, Start Year, DepcNo) TRIP(SSN, From_City, To_City, Departure_Date, Return_Date, Trip ID) EXPENsE(Trip ID, Accountg, Amount) Specify the foreign keys for this schema, stating any assumptions you make.

Short Answer

Expert verified

The foreign keys in this database schema are SSN in the TRIP table and Trip ID in the EXPENSE table.

Step by step solution

Identify Primary Keys

The first task is to identify the primary keys of each table. The primary keys are unique identifiers for each record in a table. For the SALESPERSON table, SSN (Social Security Number) serves as the primary key because it is unique for every salesperson. For the TRIP table, Trip ID appears to be the unique identifier, so it is the primary key. And for the EXPENSE table, the combination of Trip ID and Accountg could serve as the primary key, assuming each expense account is only used once per trip.

Foreign Keys in TRIP Table

A foreign key in a table is a field (or collection of fields) that is primary key in another table. In our case, in the TRIP table, SSN is a foreign key. It is the primary key in the SALESPERSON table and links a trip to a specific salesperson.

Foreign Keys in EXPENSE Table

In the EXPENSE table, Trip ID is a foreign key because it is the primary key in the TRIP table. This foreign key relationship implies that each expense is associated with a specific trip.

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Identify Primary Keys

Foreign Keys in TRIP Table

Foreign Keys in EXPENSE Table

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