Schema (1 Viewer)

[jpk]

I was just wondering wat exactly a schema (not schematic diagram) is in a relational database..
IS it an equivalent of a file???

 

[Huy]

A schema is an organised plan of the entire database.

It shows where data is found, the descriptions of the data and the relationships between entities.

The schema defines the entities, attributes and relationships in a relational database.

Basically, it is the data definition for a database.

It is not the equivalent of a file, but is an organised plan.

(Think of a Gantt chart, it's not a "file" but it is a tool to be used, in helping to visualise or model something. In (sort of) the same way, a schema helps to define the database).

 

[jpk]

ah ok
so its like a data dictionary

 

[Huy]

Originally posted by jpk

so its like a data dictionary

Yep... it's like one, but it doesn't define the fields, it define's the entire database "as a whole", each entity, attribute and relationship.

 

[jpk]

can u give me an example of one??

 

[Huy]

Originally posted by jpk
can u give me an example of one??

Don't pay attention to the dots

Entity......................Attribute
Students.......................StudentID
.....................................FirstName
.....................................LastName
.....................................Address
.....................................Suburb
.....................................PostCode
.....................................PhoneNumber
Teachers.......................TeacherID
.....................................Teacher
.....................................PhoneNumber
.....................................Extension
Classes.........................ClassID
.....................................ClassName
.....................................TeacherID
.....................................Units
Students and Classes..StudentClassID
.....................................ClassID
.....................................StudentID