Chapter 1
Why do we say a database is "self-describing" and why is this an advantage?
: A database is considered self-describing because it contains a description of its own structure within the database itself. This description is called the metadata, and it is stored in specialized tables in relational databases. The advantage is that the database is self-documenting, and that a knowledgeable user or a database designer can easily access the metadata. All DBMS vendors provide tools to access the metadata within their products.
What are "referential integrity constraints"? Give an example.
A referential integrity constraint is a rule that restricts certain actions on the database data. A referential integrity constraint is used to ensure that the values in a field in one table have matching tables in a corresponding field in another table. These constraints are enforced by the DBMS, which will not allow changes to the values of the database that would result in violations of this rule. For example, a database has an EMPLOYEE table and a VEHICLE table that are used to store data on employees and the vehicles that they are assigned to drive. The EMPLOYEE table has a column called EmployeeID that is used to distinguish one employee record from another. The VEHICLE table also has an EmployeeID column that is used to associate a vehicle with the appropriate employee. A referential integrity constraint could be used to prevent a vehicle from being assigned to an employee with an EmployeeID that does not appear in the EMPLOYEE table by requiring that all values in EmployeeID in the VEHICLE table have a matching value in EmployeeID in the EMPLOYEE table.
Microsoft Access may use which of the following DBMS engines?
A) ADE B) SQL Server
Which of the following are basic components of an enterprise-class database system?
A) The user B) The database application C) The database management system (DBMS) D) The database
Microsoft Access includes:
A) a DBMS. B) an application generator.
In an enterprise-class database system, the database application ________.
A) creates queries B) creates forms
A database consists of integrated tables, which store ________.
A) data B) relationships among the data
Database professionals use ________ as specific data sources for studies and analyses.
A) data marts
A database stores:
A) data. B) relationships. C) metadata.
A database records:
A) facts. B) figures.
A database designed using spreadsheets from the Sales department is a database being designed ________.
A) from existing data
A database may be designed ________.
A) from existing data B) as a new systems development project C) as a redesign of an existing database
The purpose of a database is to:
A) help people keep track of things.
In database systems, the database ________.
A) holds user data B) holds metadata C) holds indexes D) holds stored procedures
In database systems, the DBMS ________.
A) inserts data B) modifies data C) reads data D) deletes data
A sales contact manager used by a salesperson is an example of a(n) ________.
A) single-user database application
A database may contain ________.
A) tables B) metadata C) triggers D) stored procedures
The relational model ________.
A) was first proposed in 1970 B) was developed by E. F. Codd C) was developed at IBM D) resulted in the DBMS product DB2
A program whose job is to create, process and administer databases is called the ________.
B) Database Management System
A database designed to implement requirements for a reporting application needed by the Sales department is a database being designed ________.
B) as a new systems development project
Database professionals use a set of principles called ________ to guide and assess database design.
B) normalization
In an enterprise-class database system, reports are created by ________.
B) the database application
Modern microcomputer personal DBMS products ________.
B) were essentially killed off by Microsoft Access
The industry standard supported by all major DBMSs that allows tables to be joined together is called ________.
C) Structured Query Language (SQL)
A database designed to combine two databases used by the Sales department is a database being designed ________.
C) as a redesign of an existing database
An online drugstore such as Drugstore.com is an example of a(n) ________.
C) e-commerce database application
A database is considered "self-describing" because ________.
C) it contains a description of its own structure
In database systems, the DBMS enforces rules which user can perform which action when. The rules are know as ________.
D) concurrency control
A very popular development technique used by database professionals for database design is known as ________.
D) entity-relationship data modeling
What are the three types of database design situations?
Database designs can be based on (1) existing data, (2) new systems development and (3) database redesign. Database designs from existing data may be based on data in spreadsheets or other data tables, or on data extracted from other databases. New systems development gathers user requirements for needed applications and designs a database to meet those requirements. Database redesign may be needed to migrate existing databases to a newer DBMS, or to integrate multiple existing databases.
In database systems, the DBMS enforces rules about which data can be written in certain columns. The rules are know as ________.
E) referential integrity constraints
What is "metadata" and how does it relate to the definition of a database?
Metadata is data about the structure of the database itself. This includes data about the names of all the tables in the database, the names of all the columns in each of the tables, the data type of each column in each table, the properties of the tables and the columns, etc. Metadata accounts for the "self-describing" aspect of the definition of a database as a "self-describing collection of integrated tables."
Briefly describe the function of the DBMS in a database system.
The DBMS creates the database and the tables and structures within it. The DBMS also reads and updates the database data. It receives requests from application programs to perform data maintenance tasks. These requests are translated into actions that are performed on the database. In addition to maintaining the user data within the database, the DBMS also maintains the database structures. The DBMS also enforces any rules that have been defined to govern the values of the data, such as data type requirements and referential integrity constraints. The DBMS controls concurrency issues, which deal with the unwanted interruption of one user's work by another user's work. As the only point of entry into the database, the DBMS also provides security for the database to restrict users' access to only the data that they have authority to read or modify. Finally, the DBMS is responsible for the creation of backup copies of the database data and for restoring the database in case a recovery is required.
Briefly describe the function of an application program in a database system.
The application program is responsible for creating and processing forms. The application displays the form to the user, allows the user to complete the data entry, evaluates the form to determine which data management tasks need to be performed, and transmits the appropriate requests to the DBMS. The application creates and transmits queries. The queries are requests for data that are created in a language like SQL, and transmitted to the DBMS to have the requested data returned to the application program. The application also creates and processes reports. The query to retrieve the necessary data for the report is sent to the DBMS. When the DBMS returns the needed data, the application manipulates it as necessary to create the requested report. The application program also applies application logic to control the manipulation of data in accordance with the business rules. Finally, the application program is responsible for providing control. Control must be exercised to allow the users to make choices for functions and tasks as appropriate for their jobs. Also, control must be exercised to manage the activities of the DBMS.
What components are included in a database?
The database contains user data, metadata, indexes and other overhead data, and application metadata. User data is the data from the user's environment that they want to track. Metadata is data about the structure of the database. Indexes and other overhead data are structures that the database uses to improve performance. Finally, the application metadata is data about forms, reports, and other application components that some databases, particularly those created with desktop DBMS products, store with the database.
What are the four components of a database system?
The four components in a database system are: the user, the database application, the database management system (DBMS) and the database. The user interacts with the database application, which interacts with the DBMS, which controls the database. The functions of the database application include creating and processing forms, creating and transmitting queries and creating and processing reports. The DBMS creates databases, tables and supporting structures, manages database data, enforces rules and provides security. The database stores the user data, the database metadata, indexes, triggers, stored procedures and application metadata.
Briefly describe the history of database processing.
The predecessor of database processing was file processing, where data were maintained on magnetic tape. Database processing as we know it today became possible with the availability of direct access disk storage in the 1960s. Using this storage, both the hierarchical data model and then the network data model were developed. In 1970, E. F. Codd of IBM proposed the relational model, which is the standard model used today. Current DBMSs such as DB2, Oracle and SQL Server are based on the relational model. The appearance of microcomputer based DBMSs, in the 1980s led to a "bloodbath" from which Microsoft Access emerged as the dominant PC workstation DBMS. More recent events include the introduction of object-oriented DBMSs (OODBMSs), and the development of tools such as XML to allow the use of database systems over the Internet.
What is the purpose of a database, and how does the database accomplish this purpose?
The purpose of a database is to help people keep track of things. It accomplishes this purpose by storing data in tables. Each table has rows and columns, similar to a spreadsheet. A database usually has multiple tables in order to keep track of different but related things. For example, we might have a CUSTOMER table to keep track of customers and a PRODUCT table to keep track of the things we sell. Each row in each table holds data about a particular instance, i.e., one customer or one product. The database also stores the links between the tables, so that we can track which customers bought which products (note: this will require an additional table if one customer can buy more than one product and one product can be sold to more than one customer).
