Database Reference
In-Depth Information
Figure 3.2
Related Tables
Interconnect and
Save Space.
A database can interconnect tables
. Relationships between tables can be
defined in the database to enforce integrity rules called
constraints
(rules that make sure connections between tables are valid). Figure
3.2 shows three tables that are related to one another. An integrity
rule for these tables would make sure that every CD in the INVEN-
TORY table, for example, is connected to a CD in the CD table.
A database saves space by relating data rather than repeating data
. For
example, in Figure 3.2, the title, label, and artist are listed in the CD
table. The CD_ID in the fifth row of the INVENTORY table is 100.
By looking back at the CD table row for ID 100, you know that the
CDRock store has 44 copies of “Soak Up The Sun” by Sheryl Crow
on the A&M record label.
All tables have columns, and all columns have a name and a datatype.
The column's name must be unique within the table and must comply with
Oracle's naming standards.
In a nutshell, Oracle's naming standards are as follows:
The name should be 1 to 30 characters long.
The name is interpreted as uppercase (unless enclosed in double
quotes).
