Basic Concepts of RDBMS

A relational database management system (RDBMS) is a group of tools and features that enables IT teams and other users to build, maintain, and interact with relational databases in various ways. Most commercial relational database management systems (RDBMS) use Structured Query Language (SQL) to access the databases, which are stored as tables in RDBMS. However, SQL is not required for RDBMS use because it was created after the relational model was first developed.

The RDBMS is the most widely used database system among businesses worldwide. It offers a combination of system performance and simplicity of implementation, and a dependable method of storing and retrieving massive amounts of data.

What is a Table?

An RDBMS stores the data in database objects referred to as tables. This table, which has many columns and rows, is essentially a collection of related data entries. Each table in a database is composed of a set of columns, each of which represents a particular attribute or field of the data being stored. Each row in the table represents a single instance of the data being stored, with each column of the row containing a specific value for that instance. Example:

What is a Tuple?

A tuple in a relational database is a single table row that symbolizes a particular instance of the data being stored. A tuple consists of a collection of attributes, where each attribute stands for a distinct quality of the instance it is used to describe.

For example in the above table, the following is a tuple:

Sai

25

Male

Mumbai

What is an Attribute?

An attribute in a relational database is a named column of a table that represents a particular property or bit of information about the instances kept in the table. There is a defined data type for each attribute that indicates the kind of information that can be kept in that column, such as text, numbers, dates, or Boolean values.

Attributes can also have constraints that specify rules for the data stored in that column. For instance, an attribute might only permit text values that fall within a specific length or a specific range of numeric values. Data integrity is ensured, and data entry errors are reduced with the aid of constraints.

For example, the City is an attribute for the above-mentioned table:

City

Hyderabad

Mumbai

Chennai

Delhi

What is a Relational Schema?

A relational schema in an RDBMS is a formal description of a table’s or relation’s structure. It provides information about the table’s name, the names and data types of its columns and attributes, as well as any restrictions or guidelines that apply to the data in the table.

What is a Relation Key?

The column or set of columns in a table that uniquely identifies each row or record in the table is known as the relation key. In order to ensure data consistency and integrity within the database, relationships between tables are established using the relation key.

Relational Integrity Constraints:

The Relational Integrity Constraints are a set of rules that every relation in a relational database model must adhere to in order to be considered valid.

There are several types of integrity constraints, including:

• Entity integrity: Ensuring that each row in a table is distinct and can be located by a primary key is known as entity integrity. A column or set of columns known as a primary key uniquely identifies each row in a table.
• Referential integrity: Referential integrity verifies the validity of the connections between tables. A column or group of columns in one table that refers to the primary key of another table is known as a foreign key. A foreign key ensures that the values in the column(s) must coincide with the values in the column(s) serving as the primary key of the other table.
• Domain integrity: Domain integrity guarantees that the information stored in each table column is of the right data type and falls within the acceptable range of values. Usually, data validation and data type checking are used to enforce this.
• A key constraint in a relational database is a regulation that details which attribute in a table can be used to specifically identify each row in the table. Each row in the table can be identified using a key, which is a collection of one or more attributes. Since a NULL value indicates that an attribute’s value is unknown or undefined and cannot be used to uniquely identify a row, the key attribute(s) should never be NULL.

Note: also read about Codd’s Rule for Relational DBMS

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