#12 Databases

1. Define a relational database.

• A. A set of organised information held in a table
• B. An organised, persistent store of data organised into related tables
• C. A set of tables and validation rules
• D. A structured collection of tables where blank fields are not allowed

2. How does a flat file differ from a relational database?

• A. All data is held in one table, causing data redundancy
• B. Data is held in one table but validation rules cannot be applied
• C. It is not possible to query (or filter) data in a flat file database
• D. Searches for data are much faster in a flat file database

3. What is a primary key?

• A. It is a unique identifier for each record in a database
• B. It is a unique identifier for each field in a database
• C. It is a unique identifier for each field in a table
• D. It is a unique identifier for each record in a table

4. Which of the following could make a suitable primary key in a table of adult residents of a town?

• A. Gender
• B. Landline phone number
• C. Surname
• D. National Insurance number

5. How are foreign keys used in relational databases?

• A. They act as a validation rule, ensuring the right type of data is input
• B. They act as a referential constraint, cross-referencing to a record in another table to prevent data redundancy
• C. They uniquely identify each record in a table
• D. They allow two or more field values to jointly uniquely identify a record within a table

6. If a table called CUSTOMERS has a primary key called CustomerNumber and a separate table called SALES has a foreign key called CustomerToCharge, which of these is true?

• A. The value of CustomerToCharge is a cross-reference to one of the values of CustomerNumber in the CUSTOMERS table, and referential integrity will check that any values entered for CustomerToCharge already exist in the CUSTOMERS table somewhere in the CustomerNumber column
• B. All values of the primary key column CustomerNumber must be used at some point in the CustomerToCharge column
• C. All values of the foreign key column CustomerToCharge must be unique in the SALES table
• D. Referential integrity cannot be applied to this scenario because there is a one-to-many relationship between the two tables

7. When a non-key column/field is used as a secondary key, which of these advantages is derived?

• A. It speeds up searches when the non-key column is searched because it is now indexed
• B. It applies the rule that all values in the non-key column must now be unique
• C. It means that the index on the secondary key column will be reconstructed each time the table changes
• D. The table now benefits from having two primary keys

8. Which of the following is not shown on an ER diagram?

• A. Entity names
• B. Primary keys
• C. Validation rules
• D. Relationships

9. What is data redundancy?

• A. The construction of a relationship between two tables
• B. The correctness of data
• C. The unnecessary repetition of data
• D. The use of a composite key

10. Which of the following is not a method for capturing data to be stored in a database?

• A. OMR
• B. OCR
• C. MICR
• D. ACID