What types of relational databases are there?

Relational databases are divided into five types based on data models and structures: 1. Hierarchical database: hierarchical structure, fast query speed; 2. Mesh database: flexible connection, processing complex relationships; 3. Relational database: relationship Model, easy to use; 4. Object database: object-oriented programming concept, improves code reusability; 5. NoSQL database: flexible storage, suitable for big data and unstructured data.

Classification of relational databases

Relational databases can be divided into the following types according to their data models and structures:

1. Hierarchical database

• organizes data into a hierarchical structure, in which each node can have multiple sub-nodes.
• Use pointers to connect nodes to achieve association between data.
• Advantages: Fast query speed, suitable for processing hierarchical relationship data.
• Disadvantages: Data update and delete operations are complex.

2. Mesh database

• is similar to a hierarchical database, but the connections between nodes are more flexible.
• Use pointers to connect data, but a node can have multiple parent nodes and child nodes at the same time.
• Advantages: The data structure is flexible and suitable for processing complex relationships.
• Disadvantages: Data management and maintenance are complex.

3. Relational database

• adopts a relational model to store data in tables.
• Each row in the table represents a record, and each column represents an attribute.
• Realize the association between data through primary keys and foreign keys.
• Advantages: Simple and easy to use, strong data independence, convenient query and update operations.
• Disadvantages: The performance when processing complex relationships is not as good as hierarchical and mesh databases.

4. Object database

• stores data in object format.
• Supports object-oriented programming concepts such as encapsulation, inheritance and polymorphism.
• Advantages: It is more in line with the object-oriented programming way of thinking and improves code reusability.
• Disadvantages: Performance may not be as good as relational databases.

5. NoSQL database

• does not follow the traditional relational data model.
• According to different data structures and access modes, it is divided into key-value database, document database, wide column database, etc.
• Advantages: Flexible data storage, strong scalability, suitable for processing big data and unstructured data.
• Disadvantages: Data consistency guarantee is not as good as relational database.

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