Briefly describe the application scenarios of relational database and NOSQL database respectively.

Relational database management system (RDBMS) is a database management system that uses relational models to organize data. It is a traditional and most commonly used database type, which is widely used in various fields, such as enterprise applications, government agencies, educational institutions and so on.

Relational database is suitable for storing structured data and performing complex query operations. They provide powerful query functions and can quickly retrieve, summarize and analyze data. In addition, the relational database also supports transaction processing, constraints, indexing and other functions, which can ensure the integrity and consistency of data.

NOSQL (not only SQL) database is a non-relational database, which aims to provide a higher performance and more flexible data model for large-scale data storage and processing. NOSQL databases are mainly divided into four categories: key value storage database, document database, column storage database and graphic database.

NOSQL database is suitable for storing unstructured or semi-structured data. They support fast writing and automatic expansion, and are suitable for the storage and processing of massive data. In addition, NOSQL database also provides flexible data simulation and query functions, which can adapt to various data types and query requirements. However, NOSQL database often does not support transaction processing and constraints, so it may not be as good as relational database in data consistency and integrity.

Generally speaking, relational database is more suitable for storing structured data, performing complex queries and transaction processing, and ensuring data consistency and integrity. NOSQL database is more suitable for storing unstructured or semi-structured data for large-scale data storage and processing.