Week 2 -Chapter 3 Flashcards
Used extensively in mathematics to provide a framework in which an assertion (statement of fact) can be verified as either true or false
Predicate Logic
A part of mathematical science that deals with sets, or groups of things, and is used as the basis for data manipulation in the relational model
Set Theory
In data modeling, the construct used to organize and describe and attirbutes set of possible values
Attribute Domain
Also known as an attibute domain. It is the set of allowable values for an attribute.
Domain
In the relational model, an identifier composed of one or more attributes that uniquely identifies a row, also a candidate key selected as a unique entity identifier
Primary Key PK
One or more attributes that determine other attributes.
Key
The role of a key. In the context of a database table, the statement “A determines B” inidicates that knowing the value of attribute A means that the value of attribute B can be looked up.
Determination
Within a relation R, an attribute B is functionally dependent on an attribute A if and only if a given value of attibute A determines exactly one value of attribute B. The relationship “B is dependent on A” is equivalent to “A determines B” and is written as A -> B
Functional Dependence
Any attribute in a specific row whose value directly determines other values in that row
determinant
Any attribute whose value is determined by another attribute
Dependent
A condition in which an attribute is functionally dependent on a composite key but not on any subset of the key
Full functional dependence
A multiple attribute key
Composite key
An attribute that is part of a primary key
Key attribute
An attribute or attributes that uniquely identify each entity in a table
superkey
A minimal superkey; that is, a key that does not contain a subset of attributes that is itself a superkey
candidate key
The property of a relational table that guarantees each entity has a unique value in a primary key and that the key has no null values
Entity Integrity
The absence of an attribute value. Note that a ____ is not a blank
Null
A primary key from one table that is placed into another table to create a common attribute. The values in the __________ must be constrained to ensure referential integrity.
Foreign key FK
A condition by which a dependent tables foreign key entry must have either a null entry or a matching entry in the primary key of the related table.
referential integrity
A key used strictly for data retrieval purposes that does not require a functional dependency. For example, customers are not likely to know their customer number (PK), but the combination of last name, first name, mi, and telephone number will probably match the appropriate table row.
Secondary Key
Special codes implemented by designers to trigger a required response, alert end users to specified conditions, or encode values. ____ may be used to prevent nulls by bringing attention to the absence of a value in a table.
Flags
A set of mathematical principles that form the basis for manipulating relational table contents; the eight main functions are: SELECT, PROJECT, JOIN, INTERSECT, UNION, DIFFERENCE, PRODUCT, DIVIDE
RELATIONAL ALGREBRA
Short for relation variable, a variable that holds a relation. A _____ is a container (variable) for holding relation data, not the relation itself.
RELVAR
A property of relational operators that permits the use of relational algebra operators on existing tables (relations) to produce new relations
Closure
A SQL command that yields the values of all rows or a subset of rows in a table. The ______ statement is used to retrieve data from tables. In relational algebra, ______ is an operator used to ____ a subset of rows. aka RESTRICT
SELECT
In relational algebra an operator used to select a subset of columns.
PROJECT
In relational algebra, an operator used to merge (append) two tables into a new table, dropping the duplicate rows. The tables must be union-compatible.
UNION
Two or more tables that have the same number of colums and the corresponding columns have compatible domains.
Union-Compatible
In relational algebra, an operator used to yield only the rows that are common to two union compatible tables.
INTERSECT
In relational algebra, an operator used to yield all rows from one table that are not found in another union-compatible table.
DIFFERENCE
In relational algebra, an operator used to yield all possible pairs of rows from two tables
PRODUCT
In relational algebra, a type of operator used to yield rows from two tables based on criteria. There are many types of ____ natural, theta equi___, and outer
JOIN
A relational operation that yields a new table composed of only the rows with common values in their common attributes.
natural join
Columns that are used in the criteria of join operations. The ________ generally share similar values
join columns
A join operator that links tables based on an equality condition that compares specified columns of the tables
equijoin
A join operator that links tables using an inequality comparison operator (<. >, <=, >=) in the join condition.
theta join
A join operation in which only rows that meet a given criterion are selected. The criterion can be an equality condition (natural join or equijoin) or an inequality condition (theta join). The most commonly used type of join.
Inner Join
A join operation that produces a table in which all unmatched pairs are retained; unmatched values in the table are left null.
Outer Join
A join operation that yields all the rows in the left table, including those that have no matching values in the other table.
left outer join
A join operation that yields all of the rows in the right table, including the ones with no matching values in the other table.
right outer join
In relational algebra, an operator that answers queries about one set of data being associated with all values of data in another set of data.
DIVIDE
A detailed system data dictionary that describes all objects in a database
System Catalog
The use of the same name to label different attributes. Should generally be avoided.
Homonyms
The use of different names to identify the same object, such as an entity, an attribute, or a relationship; should generally be avoided
Synonyms.
An entity designed to transform an M:N relationship into two 1:M relationships. The composite entity’s primary key comprises at least the primary keys of the entities that it connects.
Composite entity, associative entity, bridge entity
In the relational model, a table that implements an M:N relationship
Linking table
An ordered array of index key values and row ID values (pointers). ______ are generally used to speed up and facilitate data retrieval
Index, Index Key
An index in which the index key can have only one associated pointer value (row)
Unique index
