The Relational Database Model
a entity designed to transform an many to many relationship in two one to many relationships (see composite entity)
in data modeling, the construct used to organize and describe an attribute's set of positive values (see domain)
The composite entity's primary key comprises at least the primary keys of the entities that it connects (see composite entity)
a minimal superkey; that is a key that does not contain a subset of attributes that is itself a superkey
a property of relational operators that permits the use of relational algebra operators on existing tables(relations) to produce new relations
a entity designed to transform an many to many relationship in two one to many relationships.The composite entity's primary key comprises at least the primary keys of the entities that it connects
a multiple-attribute key
stores the data definitions as well as their characteristics and relationships.
an attribute whose value is determined by another attribute
any attribute in a specific row whose value directly determines other values in that row
the role a key. i.e. knows the value of attribute A means that the value of attribute B can be looked up
in data modeling the construct used to organize and describe an attribute's set of possible values
the property of a relational table that guarantees each entity has a unique value in a primary key and that the key had no null values
a join operator that links tables based on an equality condition that compares specified columns of the tables
special codes implemented by designers to trigger a required response, alert end users to specified conditions, or encode values.
an attribute or attributes in one table whose values must match the primary key in another table or whose values must be null
full functional dependence
a condition in which an attribute is functionally dependent on a composite key but not on any subset of the key
within a relation R an attribute B is functionally dependent on an attribute A if and only if a given value of attribute A determines exactly one value of attribute B.
the use of the same name to label different attributes
an ordered array of index keys values and row ID values(pointers) indexes are generally used to speed up and facilitate data retrieval.
indexes are generally used to speed up and facilitate data retrieval.(see index)
a join operation in which only rows that meet a given criterion are selected. Most commonly used join.
columns that join two tables. The join columns generally share similar values.
a entity identifier based on the concept of functional dependence ; keys may be classified in several ways.
The attributes that form a primary key.
left outer join
in a pair of tables to be joined, a join that yields all the rows in the left table, including those that have no matching values in the other table
in the relational model a table that implements an many to many relationship
a relational operation that links tables by selecting only the rows and common values in their common attributes.
In sql, the absence of an attribute value. note that a null is not a blank.
a relational algebra JOIN operation that produces a table in which all unmatched pairs are retained.; unmatched values in the related tables are left null.
Used extensively in mathematics to provide a framework in which an assertion(statement of fact) can be verified as either true or false.
in relational model, an identifier composed of one or more attributes that uniquely identifies a row.
a condition by which a dependent table's foreign key must have either a null entry or a matching entry in the related table. Even though an attribute may not have a corresponding attribute.
short for relation variable, a variable that holds a relation. a relvar is a container (variable) for holding relation data,not the relation itself
right outer join
in a pair of tablesto be joined a join that yields all of the rows in the right table, including ones with no matching values in the other table.
A key used strictly for data retrieval purposes. for example customers are not likely to know their customer numbers.
a path of mathematical science that deals with sets, or groups of things and is used as the basis for data manipulation in the relational model.
an attribute or attributes that uniquely identify each entity in a table
the use of a different word to identify the same object.
a detailed system data dictionary that describes all objects in a database
a join operator that links tables using an inequality comparison operator. in the join condition.
in the relational model a table row.
Two or more tables that share the same column names and have columns with compatible data types or domains.
an index in which the index key can have only one associated pointer value (row)