to Introduction Database Design workshop: March 22-23, 1999 Glossary of Database Terminology Attribute: A characteristic of an entity that we want to record or track or retrieve later; a fact about an object we're interested in. Business Rule: A statement that imposes some form of constraint on elements within a field specification, or on a relationship between two tables Data: values stored in a database. Data integrity: Refers to the validity, accuracy, and consistency of the data in a database. Entity: A person, place, thing, or event about which we want to record information; an object we're interested in. Entity-Relationship Diagram (ERD): Identifies the data / information required by the business by displaying the relevant entities and the relationships between them. Field: The smallest structure in a relational database, used to store the individual pieces of data about the object; stores a single fact about an object that we're interested in; represents an attribute. Goals of the database design process: understand your data and why you're tracking it eliminate duplication of data eliminate redundant data eliminate meaningless data or data we don't care about promote accuracy of data promote consistency of data make sure we can retrieve the information we need from the database support the business functions that use the database build a database that lends itself to future growth Key: a field in the database (or an attribute in an ERD) that is used to uniquely identify records and establish relationships between tables or entities; used for the retrieval of data in the table. Primary Key: uniquely identifies each record in a table, the field lives in the table for which it operates. Foreign Key: A key from another table that is used to define a relationship to another record in another table. It has the same name and properties as the primary key from which it is copied. Glossary of database terminology Page 1 3/19/99
Ideas excerpted and summarized from Hernandez, Database Design for Mere Mortals, Addison-Wesley, 1998
Rules for foreign keys: 1-1: Primary key from the main table is inserted into the second 1-Many: table Primary key from the "1" table gets inserted into the "many" table Many-many: Primary key from each side gets placed into a third intermediate linking table that (usually) includes nothing but both keys. Non-key: a "regular" field; describes a characteristic of the table's subject. Mission statement: Declares the specific purpose of the database in general terms, it is concise and unambiguous, does not define itself with examples or specific tasks. Objective: Defines a single general task, with no unnecessary detail Record: A single "row" in a table; represents the collection of information for a single occurrence of the entity that the table represents. Relational database: A data structure through which data is stored in tables that are related to one another in some way. The way the tables are related is described through a relationship (see below). Relationship: Establishes a connection or correspondence or link between a pair of tables in a database, or between a pair of entities in an entity-relationship diagram (ERD). One-to-one relationship: A single record in table A is related to only one record in table B, and vice versa. One-to-many relationship: A single record in table A can be related to one or more record...