I used asp.net core version 2.1 
 sqlite 
 before the database was used, I added several data structures to XXXContext AAA BBB CCC 
 in the Nuget console and entered the command 
 Add-Migration test 
 and Update-Database 
 sqlite successfully created all the data structures of XXXContext 
 now I have added a new data structure in XXXContext YYYY 
 in the Nuget console and enter the command 
 Remove-Migration 
 Add-Migration test 
 and Update-Database 
 the result will report an error 
 SQLite Error 1: "table "AspNetRoles" already exists". 
besides, if I want to modify a field of a data structure in XXXContext, how do I Synchronize to the database after modification
