To use the lightweight database sqlite in the Unity project, in addition to importing sqlite3.dll, you also need to import Mono.Data.Sqlite.dll and System.Data.dll (not required when there is System.Data.dll in the project or editor) Two files.
If "DllNotFoundException: sqlite3" error occurs when running in the editor, most of the reasons are due to the lack of relevant class libraries in the system, or the class libraries do not match. There are two solutions:
1) Download the professional version of the system from the Microsoft official website, and then reinstall it. Reinstalling using Microsoft's official system files can also solve the problem of lack or mismatch of various other class libraries.
2) Install sqlite. (Remember to put the downloaded sqlite3.dll into the Plugins folder x86/x64 folder)
