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51 Cards in this Set
- Front
- Back
Analytical database |
AKA Transactional DB. Used to support operations |
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Composite key |
multiple attribute key |
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data dictionary |
DBMS component that stores metadate (data about data) |
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dependent |
attribute whose value is determined by another attribute |
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determinant |
attribute in a specific row whose value directly determines other values in that row |
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determination |
The role of a key. A determines B indicates that knowing the value of A means that the value of B can be looked up |
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entity integrity |
in a relational table, each entity has a unique value in a primary key and that the key has no null values |
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flags |
special codes that trigger a response, alert to specific conditions, or encode values. Can be used to prevent nulls |
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foreign key |
attribute or attributes in one table whose values match the primary key in another table |
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homonym |
use of the same name to label different attributes. Avoid is possible |
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index |
ordered key values and row ID values. used to speed up data retrieval |
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inner join |
join function where only rows that meet a criteria are selected. most common used join |
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key attribute |
attributes that form a primary key |
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left outer join |
join that yields all rows in the left table, even ones that do not have matching rows |
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linking table |
table that implements an M:M relationship |
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natural join |
links tables by selecting only the rows w/ common values |
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null |
abscence of an attribute. null is not blank |
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outer join |
JOIN function that retains all unmatched paris. |
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referential integrity |
a dependent table's FK must have either a null entry or a matching entry in the related table. |
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right outer join |
join that yields all of the rows in the right table even if they don't have matching rows in the left table |
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relvar |
short for relational variable. relvar is a container for holding relational data, not the relation itself |
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secondary key |
key used only for data retrieval purposes |
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superkey |
attribute(s) that uniquely identify each entity in a table |
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synonym |
use of different names to identify the same object. avoid |
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system catalog |
data dictionary that describes all objects in a DB |
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tuple |
table row |
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union-compatible |
two or more tables that have the same column names and have columns with compatible data types |
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cardinality |
property that assigns a specific value to connectivity and expresses the range fo allowed entity occurrences associated witha single occurence of the related entity |
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composite attribute |
attribute that can be further subdivided |
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derived attribute |
does not physically exist. found using formulas |
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existence dependent |
entity whose existence depends on one or more other entities |
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existence indpendent |
entity that can exist apart from one or more related entities |
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identifying relationship |
relationship where related entities are dependent. also called strong relationship |
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non-identifying relationship |
relationship where the pk of the dependent entity does not contain the pk of the related partent entity |
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relationship degree |
number of entities or participants associated with a relationship (unary, binary, ternary, or tertiary) |
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simple attribute |
attribute that cannot be subdivided into meaningful components |
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strong entity |
entity that is existence-independent |
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weak entity |
entity that is existent dependent and has the same pk as its parent entity |
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design trap |
when a relationship is improperly identified and therefore is representated in a way that is not consistent with the real world. most common is a fan trap |
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disjoint/non-overlapping subtype |
a unique and non-overlapping subtype entity set |
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eer diagram (eerd) |
relationship diagram, provides semantic content and relationships |
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entity subtype |
subset of an entity supertype. supertype contains the common characteristics and the subtype contains the unique characteristics |
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entity supertype |
generic entity type that contains the commong characteristics of entity subtypes |
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extended entity relationship model (EERM) |
result of adding semantic constructs (entity supertypes, subtypes, clustering) to the original relationship model |
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natural key (natural identifier) |
identifier for real world objects. familiar to end users and forms part of their day-to-day busines vocab |
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overlapping subtype |
each entity instance fo the supertype can appear in more than one subtype |
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specialization |
grouping of unique attributes |
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specialization hierarchy |
hierarchy based on the top-down process of identifying lower-level. grouping by unique characteristics |
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surrogate key |
system assigned pk, usually numeric and auto-incremented |
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time-variant data |
data whose values are a function of time. |
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total completeness |
in a generalization/specialization hierarchy, condition in which every supertype occurence must be a member of at least one subtype |