What is meant by a Relational table?

Answer 1

A relational table is a storage structure in a Relational Database Management System (RDBMS). A table consists of rows and columns. Each row is one record in the table and a column refers to the attributes/characteristics that are stored for each record. Unique identifier values are used for records so records in one table can be associated (related) with specific records in another table. Below is an example to explain this.

If you are tracking business contacts and want to track their name, email address, the name of their company and the address of the company's headquarters. If you were to do this in a spreadsheet, you would create column headings for the person's Name, Email Address, Company Name, Company HQ Address. However, if more than one person works at the same company, you have to store the Company Name and HQ Address multiple times. That is, in the record for each person at that company.

In a RDBMS, a relational table is created for Contact and another for Company. The Contact table would have columns for Contact ID, Name, Email Address and Company ID. The Company table would have columns for Company ID, Company Name and HQ Address. Instead of storing the Company information multiple times, you store the information for each Company in only one record. In the Contact table, you put the Company ID value for the Contact's Company in the Contact table's Company ID column.

Now, if the company moves, you only have to change one record in the Company table and all the Contact information is automatically associated with the right address. When the RDBMS gathers the contact information together, the Company ID serves as a pointer to the location of the Company information "related" to the contact.