| Lesson 10 || The DESCRIBE Command |
| Objective || Server Manager's DESCRIBE command to show structure |
Oracle DESCRIBE Column
Viewing a list of columns
Use Server Manager's DESCRIBE command to show the structure of a table.
A very useful Server Manager command is the
DESCRIBE is usually used to view a list of columns in a database table or view.
A datatype describes data, it does not store data.
You cannot store data in a NUMBER datatype, and you cannot store data in a dataype that you define.
To store data, you have to create a table that uses your datatype.
The following command creates a table named CUSTOMER .
A customer has a Customer_ID and all the attributes of a person (via the PERSON_TY datatype).
create table CUSTOMER
What happens if you describe the CUSTOMER table?
The output will show the following column definitions:
Name Null? Type
-------------- ------ -----------
The describe command shows that the Person column of the CUSTOMER table has been defined using the PERSON_TY datatype.
You can further explore the data dictionary to see the construction of the PERSON_TY datatype.
The columns of an abstract datatype are referred to as its attributes.
Within the data dictionary, the USER_TYPE_ATTRS view displays information about the attributes of a user's abstract datatypes.