the table are the same, although the field values may differ. Every employee record has a salary field, called SALARY. The values in the SALARY field can be different for each employee. Each field occupies one column and each record occupies one row. In each column of the table, you put a specific category of information for the employees, such as their ID number, first name, and position. Each row in the table contains the information relating to a specific employee, together as one record. Each record is a unique entry and is independent of any other record in the table. The EMPLOYEE table, for example, contains records for Barney Rubble and Shelly Gravel. Although both records are part of the EMPLOYEE table, the data contained within them is independent of each other. There is no relationship between Barney's and Shelly's salaries. After the analysis of the business requirements, the database design team defines the necessary tables. Different tables are created for the various groups of information. An EMPLOYEE table is created for employee information, a DEPARTMENT table is created for department information. Related tables are grouped together to form a database. For example, a personnel or human resources application database includes both the EMPLOYEE and DEPARTMENT tables and all other tables involved in the application. Primary KeysEvery table in Oracle has a field or a combination of fields that uniquely identifies each record in the table. This unique identifier is called the primary key, or simply the key. The primary key provides the means to distinguish one record from all the others in a table. It allows the user and the database system to identify, locate, and refer to one particular record in the table. The database design team determines the best candidate field for the primary key. The employee's first and last names together could be a primary key, that is until a new employee with the same name is hired. Then the k...
