MIS Quiz 3 Chapter 4

Database Administrator

(1) A person appointed to manage the databases for the firm. The DBA needs to know the technical details of the DBMS and the computer system. The DBA also needs to understand the business operations of the firm. (2) A management person in the MIS department charged with defining and maintaining the corporate databases. Maintaining data integrity is a key component of the job.

Primary key

A column or set of columns that contains data to uniquely identify each row in a relational database table. For example, each customer must have a unique identifier, possibly a phone number or an internally generated customer number.

Relational database

A database in which all data is stored in flat tables that meet the normalization rules. Tables are logically connected by matching columns of data. System data—such as access rights, descriptions, and data definition—are also stored in tables.

Query

A method of retrieving data in a DBMS. It generally uses a formal process to pose the questions (1) what columns should be displayed? (2) what conditions are given? (3) what tables are involved? and (4) how are the tables connected? See query by example and SQL.

Table

A method of storing data in a relational database. Tables contain data for one entity or object. The columns represent attributes, and data for each item is stored in a single row. Each table must have a primary key.

Normalization

A set of rules for creating tables in a relational database. The primary rules are that there can be no repeating elements and every nonkey column must depend on the whole key and nothing but the key. Roughly, it means that each table should refer to only one object or concept.

Concurrency

A situation that arises when applications attempt to modify the same piece of data at the same time. If two people are allowed to make changes to the same piece of data, the computer system must control the order in which it processes the two requests. Mixing the two tasks will result in the wrong data being stored in the computer.

Structured Query Language (SQL)

A structured query language supported by most major database management systems. The most common command is of the form: SELECT column list FROM table list JOIN how tables are related WHERE condition ORDER BY columns.

Table Relationships

Although each table in a database stores data about a specific subject, tables in a relational database such as Access, store data about related subjects. For example, a database might contain: A customers table that lists your company's customers and their addresses. A products table that lists the products that you sell, including prices and pictures for each item. An orders table that tracks customer orders. To connect the data stored in different tables, you would create relationships. A relationship is a logical connection between two tables that have a common field.

Field (Column)

Contains data about one aspect of the table subject, such as first name or e-mail address.

Record (Row)

Contains specific data, like information about a particular employee or a product.

Field Properties

Each record has a field value. For example, Contoso, Ltd. or [email protected].

Meaning of "*"

If you want to see all the columns, you can use the key word ALL or an asterisk (*).

SQL Server

Server where it is stored

one-to-many

Single record in one table is related to many records in another table

many-to-many

When a single record in table A is related to many records in Table B and a single record in table B can be related to one or more records in table A ex- order tracking databases

Foreign key

is a column (or columns) that references a column (most often the primary key) of another table. The purpose of the foreign key is to ensure referential integrity of the data. In other words, only values that are supposed to appear in the database are permitted.

Redundancy

is a system design in which a component is duplicated so if it fails there will be a backup.

Integrity

means keeping data accurate and correct as it is gathered and stored in the computer system.

Join

used to join tables together graphically