| Glossary
of Database Terminology
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Alternative Key:
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Out
of candidate keys one attribute would be selected for the Key attribute,
remaining
candidates keywill
become alternative keys. This selected
attribute is called primary key
Alternative
keys are alternatives to primary key.
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| Attribute: |
A characteristic of an entity that we want to record
or track or retrieve later; a fact aboutan object
we’re interested in.
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| Business Rule: |
A statement that
imposes some form of constraint on elements within a field specification, or on
a relationship between two tables |
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| Candidate Key:
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-
All
columns capable to become the Key
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It
can be a single attributes or combinations of attributes
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Some
entities may have more than one candidate key
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| Cardinality |
The
cardinality of a relation is the number of tuples it contains.
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| Data integrity: |
Refers to the validity,
accuracy, and consistency of the data in a database. |
| Data:
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Raw Materials with no useful meanings
Unorganized data
Collection of Facts and (or) figures
Material to be processed |
| Database
People |
| Database administrator
(DBA)
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responsible for installing, maintaining, and
configuring the DBMS software. |
| Data administrator (DA)
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responsible for organizational policies on data
creation, security, and planning. |
| Database designer
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defines and implements a schema for a database and
associated applications.
Logical database designer - interacts
with users to determine data requirements, constraints, and business rules.
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Conceptual design - independent of
any data model
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Logical design - design database in
a particular data model (e.g. relational)
Physical database designer -
implements the logical design for a data model on a DBMS. Defines indexes,
security, and constraints.
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| DBMS developer
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writes code for DBMS software. |
| Application developer
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writes applications that access the database
using the DBMS. |
| User
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uses the database directly or through applications. |
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| degree |
The degree of a relation is the number of attributes
it contains.
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| domain
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A domain is a set of allowable
values for one or more attributes.
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| 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. |
| Extension |
The extension of a relation is the set of tuples
currently in the relation.
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| 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. |
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| Information: |
-
Anything having meaning to people
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Organised material
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Processed data
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| Intension
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The intension
of a relation is the structure of the relation including its domains |
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| System: |
A
system is a collection of integrated parts which work together to achieve some
objective
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| 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. |
| Rules for foreign keys: |
1-1: Primary key from the main table is inserted into
the second table
1-Many: 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.
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| 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 |
| 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). |
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| 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 records in table B, but a single record in table B can be related to only
one record in table A. |
| Many-to-many relationship: |
A single record in table A can be related to one or
more records in table B, and vice versa. Problems with many-to-many
relationships: one of the tables will contain a large amount of redundant data,
both tables will contain some duplicate data, it will be difficult to add,
update, delete records because of the duplication of fields between tables. |
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| Table: |
The chief
structure in a relational database, composed of fields and records, whose order
is unimportant. A single table collects together all of the information we are
tracking for a single entity; represents an object or an entity. |
| Tuple |
A
tuple is a row of a relation.
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