Database Design Test Let's test how much you have learned today! 1. What is a primary key in a relational database, and what are the key characteristics of an appropriate primary key? Answer: A primary key in a relational database is a column that uniquely identifies each record in a table. An appropriate primary key should have the following characteristics: a. It should be unique, meaning that no two rows in the table have the same value in the primary key column. b. It should be non-null, ensuring that it always has a value. c. The data type of the primary key should be numeric, an integer, or a short, fixedwidth character. 2. How do data types in a database play a significant role in data representation, memory allocation, and data validation? Provide examples to illustrate their importance. Answer: Data types in a database play a significant role in data representation, memo allocation, and data validation: a. Data representation: Data types define how different types of data are stored in memory and how they are interpreted by the computer. For example, integers, floating-point numbers, characters, and strings are all represented differently in memory. b. Memory allocation: Data types determine the amount of memory allocated for each variable or data element. Using appropriate data types ensures efficien memory usage, preventing wastage or data truncation. c. Data validation and integrity: Data types enforce rules for acceptable values that a variable can hold. For instance, if a variable is declared as an integer, non-integer values are not allowed, ensuring data integrity and reducing the risk of errors. 3. In the context of entity-relationship diagrams (ERD), what is the purpose of determining entities and adding attributes to each entity? How does this contribute to effective database design? Answer: In entity-relationship diagrams (ERD), determining entities and adding attributes to each entity is essential for effective database design. Entities represent major objects within the system, and attributes define the properties or characteristics of those entities. This process helps in: a. Identifying and organizing key data elements within the system. b. Specifying what information is stored and how it relates to other entities. c. Creating a clear and visual representation of the data model for communication and design purposes. 4. Explain the role of DDL (Data Definition Language) in the context of a database. How do DDL commands like CREATE, ALTER, DROP, TRUNCATE, COMMENT, and RENAME impact the structure of database objects? Answer: In the context of a database, Data Definition Language (DDL) is used to define and modify the structure of database objects. DDL commands impact the structure of objects as follows: a. CREATE: It is used to create a new database or objects within the database. b. ALTER: It modifies the structure of an existing database object. c. DROP: It deletes objects from the database. d. TRUNCATE: It removes all records from a table, freeing allocated space. e. COMMENT: It allows the addition of comments or descriptions to objects in the data dictionary. f. RENAME: It changes the name of an object in the database.