1. Conceptual database:
- It is a high-level representation of data and relationships between them.
- It focuses on the overall structure and organization of data, without any specific details regarding implementation.
- It is usually created by business analysts and end-users.
2. Logical database:
- It is a more detailed representation of data than the conceptual model.
- It focuses on the relationships between data and how they are organized.
- It is used to map business requirements into a database design.
- It can be implemented in different database management systems (DBMS) with little modification.
3. Physical database:
- It is an implementation level of the database, where the logical model is converted to a DBMS-specific format.
- It specifies how data is stored, accessed, and retrieved on disk or other storage media.
- It includes details such as file structures, indexes, data types, and storage allocation.
4. Hierarchical database:
- It is a type of database in which data is organized in a tree-like structure with one root node and multiple child nodes.
- It allows only one-to-many relationships between entities, and every entity has a unique parent.
- It is commonly used in mainframe systems, such as IBM's Information Management System (IMS), but has been largely replaced by relational databases.
