The heart of the RDBMS is the relational data model; data is expressed in rows and columns within tables. The names and types of the columns are defined up-front and are collectively called the schema. The rows represent the data stored in the RDBMS and can be accessed using a very popular language called SQL.
In the preceding tables, each account holder has two accounts, one savings account and one current account, and each has different balances. This can be expressed in RDBMS like in the example given below. Here you can see that each account holder is given a unique key (Customer_ID), which makes querying for savings or current account balance a lot easier and faster:
In these tables, the column definitions are the schemas: for instance, the schemas of both relations Current Accounts and Savings Accounts have three columns named Acc_ID...