Let's look at the terminologies used in Relational Data Model:
- Relation refers to the table and Cardinality refers to the number of rows in the table.
- Tuples refer to the row of the table.
- Attributes refer to the column of the table.
- Degree refers to the number of columns in the table.
- Domain refers to the range of values that can be stored for an attribute.
Now the most important thing to understand in Relational Data Model is how we are going to establish a relationship between one table with one or more other tables? The two keys which play a very important role in building a relationship are the primary key and the foreign key. Let us understand these two important terms in more detail.
To build a relation of one table with another table, the table must contain one column which contains a unique key for each row of the table called the primary key. This primary key column must be present in another table as a foreign key column. We can use different kinds of JOIN operations to get the data from more than one table.
The primary key column cannot hold null values and there should be only one primary key column in each table.The foreign key column may contain null values and there can be more than one foreign key column in a single table.(alert-passed)
There are a few important properties of the Relational Data Model that we should kind in mind before we start working with the Relational Database.
- No duplicate Tuples are allowed.
- Tuples are unordered.
- Attributes are unordered.
- Attributes values are atomic.
Relational Database Management System.
A Relational Database Management System is system software that lets us Create, Update and Administer a Relational Database. RDBMS uses SQL (Structured Query Language) to access the database. The few best examples of RDBMS are Oracle, DB2, MYSQL, etc.
We will learn more about RDBMS and SQL in our next article. You can add your valuable feedback in the comment section below.
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