There may be duplicate records in some MySQL data tables, and in some cases we allow duplicate data, but sometimes we also need to delete the duplicate data.
In this section, we will show you how to prevent duplicate data in the data table and how to delete the duplicate data in the data table. You can set the specified field in the MySQL data table to PRIMARY KEY（主键） Or UNIQUE（唯一） Index to ensure the uniqueness of the data.Prevent duplicate data in the table ¶
In recent years, Geographic Information Systems (GIS) have undergone rapid development in both theoretical and practical dimensions. GIS has been widely applied for modeling and decision-making support across various fields such as urban management, regional planning, and environmental remediation, establishing geographic information as a vital component of the information era. The introduction of the “Digital Earth” concept has further accelerated the advancement of GIS, which serves as its technical foundation. Concurrently, scholars have been dedicated to theoretical research in areas like spatial cognition, spatial data uncertainty, and the formalization of spatial relationships. This reflects the dual nature of GIS as both an applied technology and an academic discipline, with the two aspects forming a mutually reinforcing cycle of progress.