What is database and SQL?

The instance has been knocked out and the book has been read.

But what is the database? Still quite confused ···

Database definition: "one or more large structured sets of permanent data, usually related to software for updating and querying data. A simple database can be a file containing many records. Each record contains the same field set and each field has a specific fixed width ."

To put it bluntly, a database is used to store data. It is like a warehouse, a warehouse that organizes, stores, and manages data according to the data structure. In the daily work of economic management, it is often necessary to put some related data into such a "warehouse" and handle the data according to the management needs. For example, an enterprise or a public institution's Personnel Department often stores the basic information of its employees (employee ID, name, age, gender, nationality, salary, and resume) in the table, this table can be viewed as a database. With this "Data Warehouse", we can query the basic information of a certain employee at any time as needed, as well as the number of employees with a certain wage range.

After understanding the meaning and usefulness of the database, how can we create and manage the database? The Database Management System (RDBMS) is used to store data. The database management system allows you to create and query databases. What we learn is SQL (Structured Query
Language), which is the most important relational database operating language. You can write SQL clauses to access data and query, update, and manage relational database systems.