In this article, we will explore the data structures commonly used in Relational Database Management Systems (RDBMS). RDBMS is a type of database management system that organizes data into tables, which consist of rows and columns.

## 1. Arrays

Arrays are a fundamental data structure used in RDBMS.

They are collections of elements of the same type, stored in contiguous memory locations. In RDBMS, arrays are often used to store fixed-sized fields such as integers or characters.

## 2. Linked Lists

Linked lists are another commonly used data structure in RDBMS.

They consist of nodes, where each node contains a value and a reference to the next node in the list. Linked lists are particularly useful for dynamic data storage as they allow for efficient insertion and deletion operations.

## 3. Trees

Trees play a crucial role in representing hierarchical relationships within an RDBMS.

The most common tree structure used is the B-tree, which allows efficient searching, insertion, and deletion operations. B-trees are balanced trees that maintain order and balance while storing large amounts of data.

### 3.1 Binary Search Trees (BST)

A specific type of tree commonly used in RDBMS is the Binary Search Tree (BST). BSTs maintain an ordering property where each node’s left child has a smaller value, and the right child has a larger value than its parent node. This property makes BSTs efficient for searching and retrieval operations.

## 4. Hash Tables

Hash tables provide fast access to data by using a hash function to map keys to array indices. They are often utilized in RDBMS for implementing index structures or handling join operations efficiently.

## 5. Graphs

Although less common, graphs can be used in RDBMS to represent complex relationships between entities. Graph data structures consist of nodes (vertices) and edges, where each edge represents a relationship between two nodes.

### 5.1 Directed Acyclic Graphs (DAG)

A specific type of graph used in RDBMS is the Directed Acyclic Graph (DAG). DAGs are directed graphs that do not contain any cycles, making them suitable for representing dependencies between entities and ensuring data integrity.

## Conclusion

In summary, various data structures are used in RDBMS to efficiently store and manage data. Arrays, linked lists, trees (including binary search trees), hash tables, and graphs (including directed acyclic graphs) all serve different purposes within the relational database model. Understanding these data structures is essential for designing efficient and scalable database systems.