C170 Data Management Applications Notes 2022 with complete solution
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C170 Data Management Applications Notes
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C170 Data Management Applications Notes
Lesson 1 - Conceptual Models
A Logical View of Data
- Placing the DBMS between the application and the database eliminates most of the file system’s inherent limitations.
- The relational model enables you to view data logically rather than physically.
Tables and Their Characteristics
- ...
c170 data management applications notes 2022 with complete solution
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C170 Data Management
Applications
Downloaded by:Evatee
lOMoARcPSD|5967629
C170 Data Management Applications
Data Management Applications (Western Governors
University)
,C170 Data Management
Applications
Downloaded by:Evatee
, lOMoARcPSD|5967629
C170 Data Management
Applications Notes
, lOMoARcPSD|5967629
Lesson 1 - Conceptual Models
A Logical View of Data
- Placing the DBMS between the application and the database eliminates
most of the file system’s inherent limitations.
- The relational model enables you to view data logically rather than physically.
Tables and Their Characteristics
- The logical view of the relational database is facilitated by the
creation of data relationships based on a logical construct known as
a relation.
- A table is perceived as a two-dimensional structure composed of rows and
columns, and is called a relation.
- As far as the table’s user is concerned, a table contains a group of
related entity occurrences, or an entity set.
- The characteristics of a relational table are:
1. A table is perceived as a two dimensional structure composed of
rows and columns.
2. Each table row (tuple) represents a single entity occurrence within the entity set.
3. Each table column represents an attribute, and each column has a distinct name.
4. Each intersection of a row and column represents a single data value.
5. All values in a column must conform to the same data format.
6. Each column has a specific range of values known as the attribute domain.
7. The order of the rows and columns is immaterial to the DBMS.
8. Each table must have an attribute or combination of attributes
that uniquely identifies each row.
Keys
- A key consists of one or more attributes that determine other attributes.
- Determination is that state in which knowing the value of one attribute makes
it possible to determine the value of another.
- Functional dependence means that the value of one or more attributes
determines the value of one or more other attributes.
- The attribute whose value determines another is called the determinant.
- The attribute whose value is determined by the other attribute is called the dependent.
- Full functional dependence is used to refer to functional dependencies in
which the entire collection of attributes in the determinant is necessary
for the relationship.
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