Fujitsu UDS/SQL V2.5 Manuel D’Utilisation
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Relational model
General information
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The following list shows the terms used in this manual and the corresponding formal terms
defined by Codd:
defined by Codd:
In the relational model, the data is managed and processed in the form of tables.
Different types of tables exist:
Different types of tables exist:
–
base tables
–
result tables
–
views
Base tables
Base tables are tables that have a fixed definition within the database. In
, the
database contains two base tables with the table names DEPARTMENT and EMPLOYEES.
A table is composed of lines and columns. The base table in the relational model is compa-
rable to the record type in the CODASYL model. A line of a table is called a record. A record
of the EMPLOYEES table contains all the information on a given employee. Instead of the
term “column”, this manual uses the term “record element”.
A table is composed of lines and columns. The base table in the relational model is compa-
rable to the record type in the CODASYL model. A line of a table is called a record. A record
of the EMPLOYEES table contains all the information on a given employee. Instead of the
term “column”, this manual uses the term “record element”.
Result tables
Querying the database yields a new table, a result table, which contains the records
returned in response to the query.
returned in response to the query.
Views
A view is a defined section of a database. A view may contain record elements and records
from one or more base tables. Views can be addressed with SQL statements in the same
way as a base table can. The use of views can afford a vast simplification of the database
interface and provide a large degree of logical data independence.
from one or more base tables. Views can be addressed with SQL statements in the same
way as a base table can. The use of views can afford a vast simplification of the database
interface and provide a large degree of logical data independence.
Term used in manual
Formal term (Codd)
table
record (row)
column, record element
value
value range
record (row)
column, record element
value
value range
relation
tuple
attribute
attribute value
domain
tuple
attribute
attribute value
domain