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Column constraint:
A column constraint defines a constraint condition on table creation. One such condition may be "each row
must have a value stored in the relevant column." Another condition may be "more than one row cannot have
the same value in the relevant column."
Table constraint
A table constraint enables the user to define whether or not a constraint is to be applied to a table. Such a constraint
may be "more than one row cannot have the same values in one or more columns." This constraint is called a unique
constraint.
[Figure: Base table format example]
View
A view is a virtual table for manipulating data. The view does not actually contain any data. A view table is equivalent
to the subtable of a base table as shown in Figure: Concept of a view. A view is defined by a view definition. A view
definition defines the following items:
Table name:
Defines the name of the view.
Column names:
Defines the names of the view columns.
View column and row definitions:
Defines which portions of a base table or view are to form a view.
[Figure: Concept of a view]
Index
An index increases the efficiency of search processing for the database data. A data manipulation is usually
accompanied by a data search using column data of a table as the search key. Thus, data search efficiency is an
important factor in judging the efficiency of a data manipulation. The user can specify whether or not to create an
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