Relational Database

Summary

This video explains the fundamentals of relational databases, focusing on tables, rows, and columns. It discusses key concepts such as the degree and cardinality of tables, and the role of primary and candidate keys in uniquely identifying records. The video also covers composite keys and the use of foreign keys to link tables together. By using examples like student and customer data, it highlights how relational databases organize and manage information effectively. The session sets the stage for further learning on SQL and how these concepts are applied in database management.

Takeaways

• 😀 Relational databases store data in multiple tables that are linked by a common field.
• 😀 A table in a relational database is also called a 'relation' and is organized into rows and columns.
• 😀 Each row in a table is called a 'record' or 'tuple' and represents one complete unit of information.
• 😀 Columns in a table are referred to as 'fields' or 'attributes' and contain one type of information.
• 😀 The 'degree of the relation' refers to the number of columns or attributes in a table.
• 😀 The 'cardinality of the relation' refers to the number of rows or tuples in a table.
• 😀 A 'primary key' uniquely identifies each row in a table and ensures data integrity.
• 😀 A 'candidate key' is any attribute or set of attributes that can uniquely identify a row in a table.
• 😀 A 'composite key' is a combination of multiple attributes that uniquely identify a row.
• 😀 A 'foreign key' is a field in one table that references the primary key of another table to establish a relationship between them.
• 😀 In a relational database, keys help prevent data duplication and enable proper linking of related data across tables.

Q & A

What is a relational database?

A relational database is a type of database where data is stored in multiple tables that are linked by a common field.

What are some popular relational databases?

Some popular relational databases include MySQL, SQL Server, Oracle, and Sybase.

What is a table in a relational database?

A table in a relational database is also called a relation. It is a dataset that is organized into rows and columns.

What are rows and columns in a table called?

In a table, rows are called records or tuples, and columns are called fields or attributes.

What does the degree of a relation refer to?

The degree of a relation refers to the number of columns (or attributes) in a table.

What does the cardinality of a relation refer to?

The cardinality of a relation refers to the number of rows (or tuples) in a table.

What is a primary key?

A primary key is a field in a table that uniquely identifies each record (or row) in that table.

What are candidate keys and how do they relate to primary keys?

Candidate keys are attributes that can uniquely identify a row in a table. One of the candidate keys is selected as the primary key, while the others are called alternate keys.

What is a composite key?

A composite key is a combination of attributes used together to uniquely identify a row in a table.

What is a foreign key?

A foreign key is a field in a table that references the primary key of another table, linking the two tables together.