AIM: Relational Model (Represent all entities in a tabular fashion. Represent all relationships in a tabular fashion).

To communicate with Oracle, SQL supports the following categories of commands: 

1. Data Definition Language:

 Create, Alter, Drop and Truncate 

2. Data Manipulation Language:

 Insert, Update, Delete and Select

 3. Transaction Control Language: 

 Commit, Rollback and Save point

 4. Data Control Language: 

 Grant and Revoke

Data type Description:

Char (Size): Stores fixed-length character data to store alphanumeric values, with a maximum size of 2000 bytes. Default and minimum size is 1 byte.

Varchar2 (Size): Stores variable-length character data to store alphanumeric values, with maximum size of 4000 bytes.
 
Char (Size): Stores fixed-length character data of length size characters or bytes, depending on the choice of national character set. Maximum size if determined by the number of bytes required storing each character with an upper limit of 2000 bytes. Default and minimum size is 1 character or 1 byte, depending on the character set.

Nvarchar2 (Size): Stores variable-length character string having maximum length size characters or bytes, depending on the choice of national character set. Maximum size is determined by the number of bytes required to store each character, with an upper limit of 4000 bytes.

Long: Stores variable-length character data up to 2GB (Gigabytes). Its length would be restricted based on memory space available in the computer.

Number [p,s]: Number having precision p and scale s. The precision p indicates total number of digit varies from 1 to 38. The scale s indicates number of digit in fraction part varies from –84 to 127. Date Stores dates from January 1, 4712 B.C. to December 31, 4712 A.D. Oracle Predefine format of Date data type is DD-MON-YYYY. 

The following are tabular representation of the above entities and relationships: